You need the password only for the data stored on the Sync server. The local data on your devices is not encrypted.
AFAIK If you’ve lost the password, there 's no way to access the data on the server. (I consider this a valuable security feature of Obsidian Sync.)
So:
- backup the vault on your laptop
- create a new synched vault with a new password
- move/copy files from the old vault to the new synched vault