Restart Photo Upload on Android App

Hello everybody,

while experiencing problems with the android-app I did several reintalls and even deleted the nextcloud user “Martin” account and added it again (using the same user-name).
Now after setting up the android-app and connecting it to the new user-account it thinks it already uploaded most of my photos of the camera. But they are no longer in my nextcloud, as I had to delete the account and set it up as a new one.
How can I make the android app restart the Uploads?
Or even better: How can I make it “forget” that it ever has been connected to an account named “Martin” and start over “fresh and new”?
Deleting all files via the android settings, uninstalling the app, remote-deleting it from within nextcloud, disconnecting and reconnecting the account all don´t do the trick.
Is there anything server-side to reset?
Thank you for your help.

Best Regards