How to repair unresponsive "Enter" key?
On my Apple wireless keyboard, the "Enter/Return" button randomly stopped working. Is there any way to repair the key?
I would see if a cotton swab that is just moist (not dripping wet) with 85% isopropyl alcohol can clean the crud around the key as it just could be getting stuck. You may need to go a bit deeper here by carefully lift the keycap to get under the key to do additional cleaning as gunk could be effecting the scissor mechanism as well underneath.
If that doesn't fix it see if the batteries leaked as the chemicals in the batteries could have damaged the conductive traces.
Sadly, these keyboard are not very serviceable. Here is the IFIXIT teardown: Apple Wireless Keyboard (A1255) Teardown. Jump down to Step15 to see how to pop the keycap.
You can only do that by replacing all the keyboard keys, where you need to be well experienced to perform the operation since there is head involved and if not well done you end up frying the chassis. The best option will be to replace with a new keyboard. If this is helpful, do not forget to mark.Tx