Add usergroup does not work as expected

Hello,
I have an auto action, type usergroup, with the trigger: users. I execute this auto action manually from the 'internal users URL'.
The action is 'Add usergroups'. I want that the action adds the group I have selected to the other groups that the users have, but the action replace the old usergroups to the new one. How can I solve issue?
Thanks in advance

Please provide a screenshot of your Global and Action parameters for your action. Below works fine in my tests.

Global
Triggers: onAfterLogin
Type: Usergroups
User: Automatic
Access: Everybody
Action
Mode: Add Usergroups
Groups: Test Group

Hello Kyle and thanks for your answer.
I tried an action with your options and this works for me, too. But I need the trigger 'users' to be able to execute the action for all users when I decide. I have attached the screenshots related. Thanks

Should be working fine then in that case. Do you have any other actions acting on the same trigger? Enable debug mode and maximum error reporting in Joomla global configuration then leave debug in your action enabled. Next run the internal users url without &format=raw and see if any errors or debug messages output.