Check the signature directly with the packaged apk, as follows:

1) Modify the suffix of apk to a. zip file and decompress it;

2) Enter the decompressed META-INF directory and file CERT. RSA will exist.

3) Open cmd in this directory and enter the command: keytool-printcert-filecert.rsa. The signatures of MD5 and SHA 1 will be displayed here.

Thank you:/blog/harvic 880925/17618743 for your comments on 12.

After a comparison, I found that the signatures are really different. After changing the signature, the problem was solved. The reason has not been studied. It is not clear whether it is because of the settings of Android Studio.