Problem with PHP Library

I used the supplied PHP tracking API wrapper library to do a bulk tracking event and I get the response:

Interestingly it worked before, but it stopped working after doing a version upgrade and migrating to a different location. Need some guidance how to possibly troubleshoot that problem.

I did some tests with Postman and with debugging enabled. Doing a single request tracking works perfectly. I take the same token and put it into a bulk tracking request and I get the error:
WARNING! token_auth = xxxxx is not valid, Super User / Admin / Write was NOT authenticated