Turvalar, I am using Android 4.1 and EN 4.5.4 but it appears that a failed sync in the app does not produce a notification in the Android notifications drop down.
Ah, nothing says "I need more patience" like quoting and replying to your own posts =) This was resolved for me by upgrading my app to 22.214.171.124 - after doing so the steps Turvalar presented were valid. Here's how it went down for me:
1. With my session still open on the mobile device, I installed the latest version from the Play store (for me, 126.96.36.199).
2. This automatically restarted the app, and when it did, the prompt for email password change came up.
3. I did this (in the mobile browser, for me Chrome Mobile) through my email account.
4. On returning to the app, it attempted to sync and I did in fact get the Android notification in the drop down that sync failed.
5. Tapping this notification prompted for the new password I issued through step 3.
6. App began sync and complete successfully.