Synchronisation is the thing you use when you want to use Avast Passwords on multiple devices (windows, mac, iOs and android are supported). Changes you do on one device is synchronised to others. Basically, if you only used Avast Passwords on one device, then you most likely didn't have synchronisation set up.
As for export, you can do a chrome format CSV export from Passwords' settings (Export section). However you need unlocked vault for that. Anyway, if you are still stuck with "enter master password" screen, but have fix applied, then the bug this fix fixed was not your problem after all and I'm afraid I can't help you.
This fix will help people that had master password set up in the past and but unchecked all checkboxes in settings' Auto-lock section. That means their vault appeared as it was "never locked" (from technical viewpoint that was never the case, but thats not important). 18.5 update broke this, so ppl got prompt to enter master password. After these ppl get the above mentioned fix, their vault should be automatically unlocked like before.