I run 1password on two windows 7 PCs and one Android 5.1 phone, syncing with Dropbox. The Android phone uses the "free" version of 1password. I changed my master password a few weeks ago from my PC, and haven't had the need to whip out my phone and use the password function until yesterday.
I tried to unlock the vault on my phone: refused to unlock. I tried the password a few times: still locked. I updated the dropbox and 1password apps to the latest android version on my phones (both of my PCs are out of date on 1password since I haven't rebooted this month and been "reminded" of the new version). Even after updating, the vault wouldn't open on my phone. The vault opens fine using the new password on both win7 PCs.
I tried using my previous vault password on the phone: that worked. I don't think my vault on the phone is outdated: I immediately checked to see if a recently-created login appeared on the phone's vault, and it was there.
1Password Version: 22.214.171.1248pc 4.3android
Extension Version: 4.5.6
OS Version: android 5.1 win-7-64bit-SP1
Sync Type: Dropbox