Hi Claire,
Welcome to Box Community and I'm here to help!
Due to the login issue that you reported, I went ahead and opened a new ticket. A member of our team will get in touch shortly and please keep an eye to your email.
Thanks for posting!
I recently updated my Box password and can no longer log in to Box within Salesforce. I can log in to Box okay, but the Box integration within salesforce prompts me to login, opens another browser tab so I can login - which I successfully do, then when I return to Salesforce it is not recognized that I have logged in. I have tried clearing browser history and cookies, different browsers, different computers - nothing has helped. Salesforce customer service sent me to contact Box, so that the Box integration team can open a ticket with Salesforce Integration. I cannot find how to contact Box customer service - just this community forum.