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Common Stock (Details Narrative) - USD ($) $ / shares in Units, $ in Thousands							1 Months Ended	4 Months Ended	12 Months Ended
	Dec. 23, 2020	Nov. 20, 2020	Sep. 18, 2020	Oct. 24, 2019	Apr. 08, 2019	Jan. 07, 2019	Jan. 31, 2021	Apr. 30, 2021	Apr. 30, 2021	Apr. 30, 2020
Common stock, par value								$ 0.001	$ 0.001	$ 0.001
Common stock, shares authorized								100,000,000	100,000,000	100,000,000
Common stock, shares issued								52,458,011	52,458,011	12,939,420
Number of common stock shares sold					1,542,000
2019 ATM Facility [Member] | Alliance Global Partners [Member]
Aggregate offering price						$ 25,000
Number of common stock shares sold						17,595,472
Proceeds from issuance or sale of equity, net of issuance costs						$ 23,400
Combined purchase price per share						$ 1.33
Payment of sales commission						$ 800
2020 ATM Facility [Member] | Alliance Global Partners [Member]
Aggregate offering price		$ 50,000
Number of common stock shares sold									17,179,883
Proceeds from issuance or sale of equity, net of issuance costs									$ 50,000
Combined purchase price per share								$ 2.91	$ 2.91
Payment of sales commission									$ 1,600
2020 ATM Facility [Member] | Alliance Global Partners [Member] | Maximum [Member]
Aggregate purchase of common stock		$ 10,000
Stock Purchase Agreement [Member] | Aspire Capital Fund, LLC [Member]
Number of common stock shares sold			6,424,205				3,722,251
Proceeds from issuance or sale of equity, net of issuance costs			$ 4,000				$ 11,800	$ 1,000
Combined purchase price per share			$ 0.63				$ 3.17
Aggregate purchase of common stock			$ 12,500
Percentage of outstanding common stock limit for shareholder approval	19.99%		19.99%
Number of shares can be issued based upon outstanding percentage			3,722,251
Number of additional shares that can be issued upon shareholder approval	9,864,706
Stock Purchase Agreement [Member] | Aspire Capital Fund, LLC [Member] | Maximum [Member]
Aggregate purchase of common stock				$ 10,000
Stock Purchase Agreement [Member] | Aspire Capital Fund, LLC [Member]
Number of common stock shares sold									5,025,000
Proceeds from issuance or sale of equity, net of issuance costs									$ 2,900
Combined purchase price per share								$ 0.57	$ 0.57

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