EDIT: I realized that the slug name was changed, which was causing the problem. Solved!
When I upload my apk generated by expo build:android, I get this error in the Google Play Console:
Upload failed
You uploaded an APK that is not signed with the upload certificate. You must use the same certificate. The upload certificate has fingerprint:
[ SHA1: blah ]
and the certificate used to sign the APK you uploaded have fingerprint:
[ SHA1: different blah ]
This only happened after I updated from SDK 29 to 30 (nothing else in app.json changed). Any help is appreciated!
EDIT: I realized that the slug name was changed, which was causing the problem. Solved!