My guess is this has something to do with the Mapillary API updates. Whilst v3 is still active (shutdown is mid-Aug), all my OAuth applications we're nuked by Mapillary last month which caused me a similar (authentication) issue.
Is the as api really free or are there free tier usage limits/non free licence restrictions on the api which aren't compatible with the image license? (Asking as I've seen this elsewhere...)
Unfortunately I've been getting a 401 for weeks now. No idea if it's me or if it's broken