A couple of suggestions I have seen work
1) make sure you have brand new fresh batteries with lots of juice - the C7 seems to need more juice to learn than for other functions
2) Try varying the distance between the remotes if a few inches doesn't work try a foot or so
3) Some codes are just hard to learn - see if the remote can learn any codes from your other remotes - try for instance learning the 1 button from your TV remote onto the 1 L key and see if that works.
Also make sure to get the FAQ and improved manual from
www.hifi-remote.com, with advanced codes you may not need to learn at all.
Jim Cruickshank