Do you mean it won't let you insert discs at all? It could be the motor that handles that part just needs to be replaced, which should be a simple fix once you have the console open. However, whether you can find replacement motors is another matter...
It could also be that the sensor which detects discs is broken.
Does it make any noise at all if you press the eject button? It could help narrow down exactly what's wrong with it.
This arises other questions:
- Are WiiU Disc Drives replaceable?
- Are WiiU Disc Drives serialised to only work on the WiiU that its originally connected to (google same issue "iPhone 5s/6/6s Fingerprint Sensor non-replaceable issue (afaik, apple already fixed this issue via iOS update)).
If answer to first is Yes, then what are the Disc Drives (except official WiiU Disc Drives specifics) that can we use to replace it?
I reckon these are both hardware (brand and model disc drives) and software specific