Convertible Instruments and Accrued Interest (Tables)
   | 
9 Months Ended | 
12 Months Ended | 
Feb. 28, 2023  | 
May 31, 2022  | 
| Convertible Instruments and Accrued Interest | 
 
 | 
 
 | 
| Schedule of information on dividends of convertible preferred stock | 
  
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
  | 
  | 
February 28, 2023  | 
  | 
May 31, 2022  | 
 
(in thousands except conversion rate)  | 
      | 
Series B  | 
      | 
Series C  | 
      | 
Series D  | 
      | 
Series B  | 
      | 
Series C  | 
      | 
Series D  | 
 
Shares of preferred stock  | 
  | 
  | 
 19  | 
  | 
  | 
 6  | 
  | 
  | 
 9  | 
  | 
  | 
 19  | 
  | 
  | 
 7  | 
  | 
  | 
 9  | 
 
Common stock conversion rate  | 
  | 
  | 
10:1  | 
  | 
  | 
2,000:1  | 
  | 
  | 
1,250:1  | 
  | 
  | 
10:1  | 
  | 
  | 
2,000:1  | 
  | 
  | 
1,250:1  | 
 
Total shares of common stock if converted  | 
  | 
  | 
 190  | 
  | 
  | 
 12,670  | 
  | 
  | 
 10,565  | 
  | 
  | 
 190  | 
  | 
  | 
 13,806  | 
  | 
  | 
 10,565  | 
 
Undeclared dividends  | 
  | 
$  | 
 14  | 
  | 
$  | 
—  | 
  | 
$  | 
 —  | 
  | 
$  | 
 10  | 
  | 
$  | 
 —  | 
  | 
$  | 
 —  | 
 
Accrued dividends  | 
  | 
$  | 
 —  | 
  | 
$  | 
 2,341  | 
  | 
$  | 
 2,594  | 
  | 
$  | 
 —  | 
  | 
$  | 
 2,014  | 
  | 
$  | 
 1,963  | 
 
Total shares of common stock if dividends converted  | 
  | 
  | 
 28  | 
  | 
  | 
 4,682  | 
  | 
  | 
 5,188  | 
  | 
  | 
 20  | 
  | 
  | 
 4,028  | 
  | 
  | 
 3,926  | 
 
 
 | 
  
  | 
  | 
As of May 31,  | 
 
  | 
  | 
2022  | 
  | 
2021  | 
 
(in thousands)  | 
      | 
Series B  | 
      | 
Series C  | 
      | 
Series D  | 
      | 
Series B  | 
      | 
Series C  | 
      | 
Series D  | 
 
Undeclared dividends  | 
  | 
$  | 
 10  | 
  | 
$  | 
 —  | 
  | 
$  | 
 —  | 
  | 
$  | 
 18  | 
  | 
$  | 
 —  | 
  | 
$  | 
 —  | 
 
Accrued dividends  | 
  | 
$  | 
 —  | 
  | 
$  | 
 2,014  | 
  | 
$  | 
 1,963  | 
  | 
$  | 
 —  | 
  | 
$  | 
 1,530  | 
  | 
$  | 
 1,117  | 
 
Shares of common stock  | 
  | 
  | 
 20  | 
  | 
  | 
 4,028  | 
  | 
  | 
 3,926  | 
  | 
  | 
 36  | 
  | 
  | 
 3,060  | 
  | 
  | 
 2,234  | 
 
 
 | 
| Summary Of outstanding convertible notes | 
  
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
 
  | 
  | 
February 28, 2023  | 
 
  | 
      | 
April 2, 2021 Note  | 
      | 
      | 
April 23, 2021 Note  | 
  | 
 
Interest rate per annum  | 
  | 
  | 
 10  | 
%  | 
  | 
  | 
 10  | 
%  | 
 
Conversion price per share upon five trading days' notice  | 
  | 
$  | 
 10.00  | 
  | 
  | 
$  | 
 10.00  | 
  | 
 
Party that controls the conversion rights  | 
  | 
  | 
Investor  | 
  | 
  | 
  | 
Investor  | 
  | 
 
Maturity date  | 
  | 
  | 
April 5, 2023  | 
  | 
  | 
  | 
April 23, 2023  | 
  | 
 
Security interest  | 
  | 
  | 
All Company assets excluding intellectual property  | 
  | 
 
 
 | 
 
 | 
| Schedule of outstanding balances of convertible notes | 
  
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
  | 
  | 
February 28, 2023  | 
  | 
May 31, 2022  | 
 
(in thousands)  | 
      | 
April 2, 2021 Note  | 
      | 
April 23, 2021 Note  | 
      | 
Total  | 
      | 
April 2, 2021 Note  | 
      | 
April 23, 2021 Note  | 
      | 
Total  | 
 
Convertible notes payable outstanding principal  | 
  | 
$  | 
 7,819  | 
  | 
$  | 
 28,500  | 
  | 
$  | 
 36,319  | 
  | 
$  | 
 9,819  | 
  | 
$  | 
 28,500  | 
  | 
$  | 
 38,319  | 
 
Less: Unamortized debt discount and issuance costs  | 
  | 
  | 
 (49)  | 
  | 
  | 
 (257)  | 
  | 
  | 
 (306)  | 
  | 
  | 
 (512)  | 
  | 
  | 
 (1,566)  | 
  | 
  | 
 (2,078)  | 
 
Convertible notes payable, net  | 
  | 
  | 
 7,770  | 
  | 
  | 
 28,243  | 
  | 
  | 
 36,013  | 
  | 
  | 
 9,307  | 
  | 
  | 
 26,934  | 
  | 
  | 
 36,241  | 
 
Accrued interest on convertible notes  | 
  | 
  | 
 3,535  | 
  | 
  | 
 5,886  | 
  | 
  | 
 9,421  | 
  | 
  | 
 2,599  | 
  | 
  | 
 3,375  | 
  | 
  | 
 5,974  | 
 
Outstanding convertible notes payable, net and accrued interest  | 
  | 
$  | 
 11,305  | 
  | 
$  | 
 34,129  | 
  | 
$  | 
 45,434  | 
  | 
$  | 
 11,906  | 
  | 
$  | 
 30,309  | 
  | 
$  | 
 42,215  | 
 
 
 | 
  
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
 
  | 
  | 
As of May 31,  | 
 
  | 
  | 
2022  | 
  | 
2021  | 
 
(in thousands)  | 
      | 
April 2, 2021 Note  | 
      | 
April 23, 2021 Note  | 
      | 
Total  | 
      | 
November 2020 Note  | 
      | 
April 2, 2021 Note  | 
      | 
April 23, 2021 Note  | 
      | 
Total  | 
 
Convertible notes payable outstanding principal  | 
  | 
$  | 
 9,819  | 
  | 
$  | 
 28,500  | 
  | 
$  | 
 38,319  | 
  | 
$  | 
 13,500  | 
  | 
$  | 
 28,500  | 
  | 
$  | 
 28,500  | 
  | 
$  | 
 70,500  | 
 
Less: Unamortized debt discount and issuance costs  | 
  | 
  | 
 (512)  | 
  | 
  | 
 (1,566)  | 
  | 
  | 
 (2,078)  | 
  | 
  | 
 (1,204)  | 
  | 
  | 
 (3,232)  | 
  | 
  | 
 (3,317)  | 
  | 
  | 
 (7,753)  | 
 
Convertible notes payable, net  | 
  | 
  | 
 9,307  | 
  | 
  | 
 26,934  | 
  | 
  | 
 36,241  | 
  | 
  | 
 12,296  | 
  | 
  | 
 25,268  | 
  | 
  | 
 25,183  | 
  | 
  | 
 62,747  | 
 
Accrued interest on convertible notes  | 
  | 
  | 
 2,599  | 
  | 
  | 
 3,375  | 
  | 
  | 
 5,974  | 
  | 
  | 
 1,258  | 
  | 
  | 
 447  | 
  | 
  | 
 302  | 
  | 
  | 
 2,007  | 
 
Outstanding convertible notes payable, net and accrued interest  | 
  | 
$  | 
 11,906  | 
  | 
$  | 
 30,309  | 
  | 
$  | 
 42,215  | 
  | 
$  | 
 13,554  | 
  | 
$  | 
 25,715  | 
  | 
$  | 
 25,485  | 
  | 
$  | 
 64,754  | 
 
 
 | 
| Schedule of reconciliation of changes to outstanding balance of convertible notes | 
  
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
 
(in thousands)  | 
      | 
April 2, 2021 Note  | 
      | 
April 23, 2021 Note  | 
      | 
Total  | 
 
Outstanding balance at May 31, 2022  | 
  | 
$  | 
 11,906  | 
  | 
$  | 
 30,309  | 
  | 
$  | 
 42,215  | 
 
Amortization of issuance discount and costs  | 
  | 
  | 
 463  | 
  | 
  | 
 1,309  | 
  | 
  | 
 1,772  | 
 
Interest expense  | 
  | 
  | 
 936  | 
  | 
  | 
 2,511  | 
  | 
  | 
 3,447  | 
 
Fair market value of shares exchanged for repayment  | 
  | 
  | 
 (2,656)  | 
  | 
  | 
 —  | 
  | 
  | 
 (2,656)  | 
 
Difference between market value of common shares and reduction of principal  | 
  | 
  | 
 656  | 
  | 
  | 
 —  | 
  | 
  | 
 656  | 
 
Outstanding balance at February 28, 2023  | 
  | 
$  | 
 11,305  | 
  | 
$  | 
 34,129  | 
  | 
$  | 
 45,434  | 
 
 
 | 
  
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
(in thousands)  | 
  | 
November 2020  Note  | 
  | 
April 2, 2021  Note  | 
  | 
April 23, 2021  Note  | 
  | 
Total  | 
 
Outstanding balance at May 31, 2021  | 
  | 
$  | 
 13,554  | 
  | 
$  | 
 25,715  | 
  | 
$  | 
 25,485  | 
  | 
$  | 
 64,754  | 
 
Amortization of issuance discount and costs  | 
  | 
  | 
 98  | 
  | 
  | 
 1,197  | 
  | 
  | 
 1,750  | 
  | 
  | 
 3,045  | 
 
Interest expense  | 
  | 
  | 
 192  | 
  | 
  | 
 2,152  | 
  | 
  | 
 3,073  | 
  | 
  | 
 5,417  | 
 
Fair market value of shares exchanged for repayment  | 
  | 
  | 
 (18,495)  | 
  | 
  | 
 (23,578)  | 
  | 
  | 
 —  | 
  | 
  | 
 (42,073)  | 
 
Difference between market value of common shares and reduction of principle  | 
  | 
  | 
 4,651  | 
  | 
  | 
 6,421  | 
  | 
  | 
 —  | 
  | 
  | 
 11,072  | 
 
Outstanding balance at May 31, 2022  | 
  | 
$  | 
 —  | 
  | 
$  | 
 11,907  | 
  | 
$  | 
 30,308  | 
  | 
$  | 
 42,215  | 
 
 
 |