Unable to create custom connector from working Postman collection

[F_Quint]

I'm trying to create a custom connector to access an API, however I cannot get it to work. I'm using Client credentials as the grant type.

In Postman I'm able to get the access token and make POST calls to this API but this does not work when trying to build the connector. 

There's an option to import a Postman collection when creating a custom connector but Power Apps/Automate requires this to be in v1 format, however, that's no longer supported by Postman (available formats are v2 or v2.1) 

Any suggestions on how to get this to work?