My phone system has been set up for years, now all of the sudden one of our offices is having a problem of calls not rolling up to the second line (which is not a DID) when the main line is busy. There are 5 phones total and they are all set up the same. LHK is 1 (which is where it should roll to). I only have the main line (and rollup) MARP'd on one phone. Is there something else I'm missing?