I can't browse files in Word online

When I use 'Draft with Copilot' in Word online and pick 'Browse files from cloud'

I get a 'Something went wrong...PrefetchFailure (NoTokenProviderForUnauthenticatedPrefetch)

I've tried resetting and deleting the cache, a new browser, and an incognito browser, but nothing works.

I'm on an E3 O365 license and have an active Copilot 365 license. I have admin rights.

How do I solve this?