2. Summary of Significant Accounting Policies (Details Narrative) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020	Apr. 30, 2020	Apr. 30, 2019
Accounting Policies [Abstract]
Revenue recognized for which the contract liability was recorded in the prior year	$ 3,500	$ 600	$ 26,300	$ 13,200
Depreciation and amortization	900	800	2,500	2,300
Impairment of long-lived assets			0	0
Restricted cash	$ 350	$ 350	$ 350	$ 350	$ 350	$ 1,150