ERROR: Unregistering runner from GitLab forbidden

Hello,
I have some questions about the GitLab-Runner:
1- If I delete a runner from the Runners section, how do I get it back?

2- I want to unregister a runner, but I get the following error message:

# gitlab-runner unregister --url https://IP --token {TOKEN}
Runtime platform                                    arch=amd64 os=linux pid=135179 revision=44feccdf version=17.0.0
Running in system-mode.                            
                                                   
ERROR: Unregistering runner from GitLab forbidden   runner=KmAJwHxz_ status=DELETE http://IP/api/v4/runners/managers: 403 Forbidden
FATAL: Failed to unregister runner 

What is wrong?
Using the gitlab-runner verify --delete command, the problem is solved, but all runners are deleted!

Thank you.