When you change the master password on a device, it is changed for the local database and for the cloud account with which Enpass has been syncing. It won't be reflected on the rest of the devices (syncing with the same cloud), because they are not aware of new password.
So during the next sync, the other devices will fetch the database from the cloud (which is now encrypted with a new password) but won't be able to open it and will end up with the message: Error syncing with cloud. Reason: Password mismatch.
Then you will get the prompt to enter the master password of Enpass data on cloud. And right after entering the new password, the downloaded database will be accessible, and sync will resume. But even after entering the password, the master-password of your local device will not been changed. So, if you want to use the same master-password on all the other devices too, you'll have to manually change them.