Entity services API - REST access

hello,

im making an app and would like to integrate a messaging functionality. so privatemsg is an obvious option.

there is the services entity module which provides a resource for this great module. but when i try to access it, i get a "access denied" message from postman (see postman screenshot) even though im accessing as admin and have all permissions. the x-csrf token is also passed along.

ive tried other entites that the services entity module provide and i can GET/retrieve them with postman. so im asking here.

thx for any info on this!