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Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands | Apr. 30, 2022 | Apr. 30, 2021
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Income Tax Disclosure [Abstract] |  |
Federal net operating loss carryforwards | $ 40,338 | $ 36,340
Foreign net operating loss carryforwards | 2,061 | 4,064
State operating loss carryforwards | 968 | 581
Federal and New Jersey research and development tax credits | 4,167 | 3,303
Stock compensation | 429 | 346
Accrued expenses | 79 | 158
Other | (445) | 545
Net deferred tax assets before valuation allowance | 47,597 | 45,337
Valuation allowance | (47,597) | (45,091)
Deferred tax assets |  | 246
Other liability | 203 | 246
Net deferred tax assets (liabilities) | $ (203) |

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