I have Google Pixel 4a with 3.0.4 and SecureGo Plus 4.2 and it also doesn’t work. 
I called my bank (GLS) a minute ago and explained this problem to the guy who’s specialist for SecureGo. Clear answer: From version 4.2 on SecureGo will NOT work without Google anymore. No chance.
I let him switch to SmartTAN Photo and that works.
Not my preferred solution but it works.