I'm currently a mechanic. When i go to change skin at the clothes store, the only skins i can choose from are 3 mechanic skins. I was told to go off-duty and then try, but when I try to do it, on the checkpoint at xoomer, I click on yes and nothing happens. No message, alert, notifications..nothing at all. I had this same issue a week ago when I decided to test out the mechanic skin and I'm still stuck with it.
I tried switching to a cop at police department, and I was able to do it. But, when i go off duty as a cop i instantly get back to the on-duty mechanic.
If it's any help, my ingame name is shades and here's a few pictures of what i described above:
https://imgur.com/a/jLsUIyjSo, long story short, as a mechanic i'm unable to go off duty and change skin/job to a normal regular civilian.