I've had it happen. It's the standard and ultimate death of these. Unlike a cable intermittency it's not repairable.
You can try the distilled water swizzle cleaning method, which has a chance of fixing them if its simply dirt or other stuff clogging the openings. The effect of which can be similar in decreased sensitivity.
If you send them to DPA they will check them, but will cut off the miniplug to do so. I've sent mics back for them to check and do that, knowing that they will not be able to fix them, just because they've always then offered to sell me a replacement directly at reduced cost. Not nearly as inexpensive as a used "Broadway" mic, but not quite as painful as buying a new one from a reseller.