When you first start at UAL you are given a temporary password which can only be used three times to log in to UAL services. Although your email will continue to work, you will not be able to access most other UAL services... including Commonplace.
You will need to visit https://pss.arts.ac.uk to change your password to something more secure. You should then be able to log in to Commonplace with your UAL ID and new UAL password. If this doesn't resolve the issue, please contact the Service Desk (firstname.lastname@example.org) for assistance.