I lost my keystore (.jks) file, and I was lucky - I used App signing before. Therefore, Google was able to help me and reset my key.
But what is the next step with the SHA1 google gave me by mail? They gave me the instruction for generating an upload_certificate.pem file that I sent them by mail.
And then, Google's answer was:
Good news - I was able to register your new upload key, you would need to update your app to use the new upload key certificate: SHA1:....
Now I try to upload the APK with the jks file I used to generate the PEM file, also with a newly created jks file. in Google play console I get:
Your Android App Bundle is signed with the wrong key. Ensure that your app bundle is signed with the correct signing key and try again
What is the next step?
After I tried everything that came in mind, including "Invalidate cache and restart" in Android studio, the solution that worked was Build->clean. Thanks to Dave Hubbard's answer