It’s still a fairly new system, so I don’t know what we can do, but a ticket is definitely the way to go.
Since the message you are getting is associated with a character boost, I’d submit your ticket using “Purchase Failure” instead of the general gameplay one you used. That way we can take a look at the character and see what can be done.
Edit: Unfortunately, it looks like our Support staff is unable to assist in this instance, so I’m editing this to discourage submitting a ticket.
This is actively being worked on though, while I don’t have any updates it remains a priority to allow folks to log into their characters as quickly as possible.