I encrypted my data without error on the desktop and then synced on the phone but old notes are not encrypted. I sync to Dropbox. Besides looking on my computer, I also went to the Dropbox web interfaced and verified old not encrypted files there. Then I tried re-encrypting and that didn't fix the issue although the procedure finished without errors. Then I decrypted and re-encrypted and that didn't fix the problem either.
I have used the searched, and haven't found the answer. Maybe I don't know what to look for.
There are no errors on the desktop or the phone. I would be glad to provide any other needed information to solve this.
Fortunately, through all of this, all of my data (encrypted or not) is always readable on the desktop and the phone.
I an running: Joplin 1.2.6 (prod, linux)