Trying to add users to my org, getting 403

I'm trying to new add users to our org, but it always fails, getting a 403 error.

From Safari's web tools:

Summary
URL: https://appstoreconnect.apple.com/iris/v1/userInvitations
Status: 403
Source: Network
Address: 23.197.246.197:443

Request
:method: POST
:scheme: https
:authority: appstoreconnect.apple.com
:path: /iris/v1/userInvitations
Accept: application/vnd.api+json
Accept-Encoding: gzip, deflate, br
Accept-Language: en-CA,en-US;q=0.9,en;q=0.8
Connection: keep-alive
Content-Length: 265
Content-Type: application/vnd.api+json
Trying to add users to my org, getting 403
 
 
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