Im holding down the ` key and hitting the appropriate paired key but CUSP doesn always respond. Why?
On many applications that use ALT, it is common to hold ALT and keep it pressed while pressing the companion key. This is not the case in CUSP. Hit ` first, release it and then hit the companion key. On the other hand, it may be possible that you have accidentially pressed the capitals lock, remember all ALT + “key” is case sensitive.