The easiest way to check if the adjustment wheel is working is to unwind in clockwise and then wind it anticlockwise whilst looking down into the burrs. You should see a gap open and close.
If the burr seems stuck when unwinding the adjustment wheel, try jiggling the main turn-handle whilst beans are in the hopper. This normally frees it.
If this doesn’t work then try Step 2.
Unwind the adjustment wheel until it comes away.. The conical burr and 'burr key’ should now drop out, but they might be stuck and need a knock on the star shaped flat area on the top of the burr. Don’t lose the spring when it drops out. Attach the 'burr key' to the conical burr. Place the spring back onto the shaft and slide on the burr/burr key assembly. This should slide up and down freely. Do this a few times to check it runs okay. Then wind the adjustment wheel back on .
If the burrs are not jammed and you can see them opening and closing, It may be that the burrs have become slightly out of alignment
You could try re-aligning the ring burr by following this method
re-align the ring burr. Instruction below -
Unwind the adjustment wheel to around 20 clicks.
Unscrew the 2 grub screws (2 rotations) located above the adjustment wheel.
Wind up the adjustment wheel to close the conical burr against the ring burr.
Rotate the main handle a quarter turn clockwise.
Tighten the 2 grub screws.
Unwind the adjustment wheel and use as normal.