We have upgraded our CRM 2015 sp1 to CRM 2016 on premise. I am finding that even as admin I can not use the assign button to assign accounts to another user. The "me" option is available but the user options has a lock on it.
If however I select the accounts I want to change ownership on and click edit and select a new owner for the owner field that works. Why would I as admin not be able to assign a contact record from one owner to another? But be allowed to change the owner field using edit to another owner.
Same thing is true for an individual Account. If I select the Assign button, I only am allowed to assign to me. But if I open the account and select a new owner with the drop down list - then the ownership changes.