I can connect to the /v1/people/~ API URL perfectly with my Access Token but trying the same Token on the /v2/adAnalyticsV2? gives me a 403 error (without further explanation). I read through all the LinkedIn documentation about their Rest API and I just don't get it.
Please help.
Based on the error code, it looks like you do not have the proper permission to access this endpoint.
Has your application been given access to use LinkedIn's Marketing Analytics API? If not, you can apply for access here: https://business.linkedin.com/marketing-solutions/marketing-partners/become-a-partner
If you already have access, you should check if your application is requesting the required permission when requesting authorization codes. You would do this either by selecting it in the Default Application Permissions section when setting up your application, or by explicitly requesting it through the scope parameter in the authorization step