Documentation
Migration
When your datastore moves to another host, or its credentials change, update the connection on your side. The datastore page shows the new details.
The PVE GUI cannot change an existing PBS storage. Edit /etc/pve/storage.cfg on your PVE host and change the details there.
To change the password, run this command. Replace <storage> with the name of your storage.
pvesm set <storage> --password
Change the credentials of the remote in the PBS GUI, or with the proxmox-backup-manager CLI. Each argument is optional:
proxmox-backup-manager remote update <name> --auth-id '<username>' --password '<password>' --host '<host>'