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Income Taxes (Details Narrative) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Apr. 30, 2021 | Apr. 30, 2020
Income tax benefits |  | $ (895)
Deferred tax assets, valuation allowance | 45,091 | 42,431
Increase (decrease) in valuation allowance | 2,700 | (700)
Net operating loss carry forwards | $ 173,000 |
Operating loss carryforwards, expiration description | Begin to expire in fiscal 2022 |
Net operating loss subject to no expiration | $ 36,600 |
Operating loss carryforwards, deductibility limitation | The deductibility of such federal net operating losses may be limited to 80% of our taxable income in future years. |
Deferred tax assets, tax credit carryforwards, research and development | $ 3,303 | 3,076
Proceed from sale of loss carryforwards and tax credits | 12,000 | 10,000
Interest or penalties accrued on uncertain tax positions |  |
Spain [Member] |  |
Income tax description | The Company is currently undergoing an income tax audit in Spain for the period from 2011 to 2014 |
Uncertain tax positions |  |
Interest or penalties accrued on uncertain tax positions |  |
Research and Development Expense [Member] |  |
Proceeds from sale of credit | 1,000 | $ 900
Research and Development Expense [Member] | New Jersey [Member] |  |
Income tax description |  | New Jersey-based technology or biotechnology companies with fewer than 225 US employees may be eligible to sell net operating losses and research and development tax credits to unaffiliated corporations, up to a maximum lifetime benefit of $20 million per business.
Research and Development Expense [Member] | New Jersey [Member] | Maximum [Member] |  |
Proceeds from sale of credit |  | $ 20,000
State and Local Jurisdiction [Member] |  |
Income tax benefits | 1,000 | $ 900
Net operating loss carry forwards | $ 21,300 |
Operating loss carryforwards, expiration description | Begin to expire in 2039, which also may be limited to utilization limitations. |
Foreign [Member] |  |
Net operating loss carry forwards | $ 18,900 |

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