I have site admin access, but I am unable to remove user from a group using Rest API, what can I do?

[Anantya Mary J]

I am trying to hit the  remove user from group  API from Postman. I have given the right API token since I am able to add a user to a group using the same token. I have also given the right accountId but I am getting this error - 

{
"errorMessages": [
"Specified user does not exist or you do not have required permissions"
],
"errors": {}
}

Please help me figure out what went wrong.

[oliver.wihler]

1. perhaps the group is not native but from a directory service?

2. can you share with us the Rest call you made with all the parameters? Except the user authentication with your token, of course you want to keep that private.