Azure Monitor- Announcing General Availability of Azure Monitor Metrics Data Plane API

Hi there, I've been trying to migrate to this API from the classic one. The same token that works for the old API is not working for this one. The error given is 401 and additionally says that the token needs to include an 'oid' field.  I am using the Go SDK with a Client Certificate credential on a service principal which has monitoring reader on my subscription, and actually I confirmed thru debugger that my token does have the 'oid' field. So perhaps the error description? I read the section about the 401 errors on the docs but didn't see anything about this. I would appreciate any assistance with this!