I have a sub with a ctx 100 system. I added a new line, line 5, to the system yesterday for one specific extension. The ext. is cf-bna to the voice mail system, ext 555. Calls coming in on lines 1-4 call forward to vm as they are supposed to. Any call coming into that ext. on line 5 just rings and never forwards. Any ideas?

There should be a setting to configure line 5 as DIL (direct inward line). Note: I'm not sure if this is Toshiba's description.
I'm more familiar with the NEC systems, we configure the line as DIL we enter the extension number giving the extension owner ship of the line so it will forward into the user mailbox instead of AA.

I hope the info above will give you a clue what to look for in the CTX100

In Toshiba, they call it DIT, Direct Inward Termination (Prg 310 under Trunk assignments). It is pretty much the same thing as the NEC. You can also assign the extension as the owner of that line in the Key assignments. When an extension is an owner of the line, then the calls will forward based on the user's call forwarding. In either case, the calls will go to the user's voicemail box and not the AA.