Strange problem with power supply

Hey, I build myself a case some months ago. I used the power supply from MDLR. Everything worked fine for quite some time. Now i wanted to play a little bit, started the modular and on first view some modules behaved strangly and i quickly realised on the power supply only the LEDs for +12 und 5v are lighting up but not for -12v. I instantly turned it off and started to take the system appart and looking for shorts or something obvious but i found nothing. Now with all modules out of the case, when i power it up it is still the same thing... LEDs on +12 and 5 but nothing on -12.

I was looking for advice online but couldn't find anything that fits my problem. Has someone here an idea what i could do?

I don't know what could cause this. Last time i played everything was fine and in between i havn't changed anything and nothing happed (i didn't moved it or something).

I'm affraid of puting modules in and powering it on but i want to play... 😄