Your admins have broken your system.
You must remove the resolution field from all of your Create and Edit screens immediately.
You should also check the list of resolutions in Admin -> Issues -> Resolution. If you have "unresolved" listed, you must rename it to something like "do not use this" immediately.
Check and fix both of these things as soon as, then we can start talking about undoing the damage in your data.
Part of the tone was because this question was posted several times by allegedly different accounts, as though a company had taken a contract to support JIRA without knowing what they were doing, and had got in loads of non-experts to do an expert's job.
Also, it clearly shows no effort to bother to search for any solution, and there's probably too little explanation of what the question really is. There are hundreds of questions here about resolutions being broken, and I wasn't going to repeat them.
The response is correct, and aimed at getting them to prevent further damage before looking at the root cause
I see... In that case I understand your tone of voice.
I did find the solution for my 'resolution'-problem, although I think sometimes it's hard to find some basic stuff like this in the Jira-documentation.
To find out that you need a Post function on a Workflow to change the resolution is quite difficult. I do understand that there are raised 'hundreds of questions' about this...
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