I have an app that has been working for two-way sync for quite sometime. Nothing has changed on my end.
Now, any PUT request is getting a 401/token_rejected. GET requests continue to work fine. Both are using HTTPS.
I should add that according to YDN at least, my project has read/write permission.
If I switch to using a Authorization header it gives: unable_to_determine_oauth_type
But otherwise it works identically. GETs work perfectly, PUTs do not. This app has been up and running for about 2 years without issue.