Your previous toot showed that the app index was not updated in years, it can't know about a recent 2.0 update if it didn't know about 1.23.2 that you had to manually update. Neither does updating the APK directly help. The index is a living thing. Go to Settings, Repos, F-Droid, what does "Last update, Last check" say?
We have better error logging in latest 2.0, so if still won't update the index: https://f-droid.org/packages/org.fdroid.fdroid/ under "Version 2.0-alpha11" press Download APK