You have MicroG installed right?
Tested from a diff device but why don't you try this fix
Just in case someone is facing an issue with a login on YT Vanced v16.02.35, follow the below steps to fix the issue:
*The microG has some incompatibility issue with YT Vanced v16.02.35, hence the signing issue.
1. Disable/Uninstall Chrome for Android.
2. Uninstall MicroG, YT Vanced, YT Vanced Music
3. Using the Vanced Manager install the Latest microG v0.2.16.204713
4. Now install YT Vanced v15.43.32
5. Open YT Vanced and signing.
6. Now you can update YT Vanced or YT Vanced Music.
Tested on Oneplus 6T ♥
Next month. currently Dev is inactive he will be back on 21st of December
Ha ha.. Updates will come soon..ZIDAN44 is not active on XDA since the end of May. Must be some personal problems. If his health permits, I'm sure he'll be back again. This kind of work is also a personal interest and pleasure of every developer. The only question is whether he will continue his original work.