The user [xxx] does not have sufficient privileges to perform the requested action.

You'll need to run this node as Admin. See Create User Smart Service - Appian 23.1

Thanks for you answer Laurens, I've run it as an administrator, but it still gives me the error. 

Have you checked if he is in the right group? Also, you need to check the security of your process models and rules to ensure you have the correct security settings for the group or user.

Have you checked if he is in the right group? Also, you need to check the security of your process models and rules to ensure you have the correct security settings for the group or user.