[![Change the build variant then you can see the run the application which will lead to error
You have to find SHA1 code for Release Key & enter it on your Developer Console. ( for me developer console is firebase some people might use different services) To find SHA1 Code . easy way is
Go to Build --- Select Build Variant -- On the left Side Select "Release" as build variant -- now go to module settings ( or try to run project , android studio will tell you about a error and click fix error button) --- Select Signing tab --- add your release key and passwords -- now goto build types -- select release -- on signing config select your release key config -- now run your project -- now run your signing report --- you can find SHA1 under release build -- enter that sha1 code on your developer console