System is a MICS 7.0 with CP100 3.1. CP100 is accessible through the LAN and configured for CallPilot mode instead of NVM. PRI with 8 channels / 10 DID's (line 157 +) and 3 I/C on each set (7316E). DN 221-228 all have VM boxes with matching box numbers.

Regardless of the origin of the call (I/C or outside line), when using F986 to transfer the caller to a VM box, the set prompts for the mailbox, flashes "Call Transferred" but then pops back to:

221 (or whatever VM box transferred TO)
DIR QUIT

and this stays on the set display until the caller disconnects. The caller is prompted with "Please enter the mailbox number or press the # sign to use the directory". I know it is trying to get to a VM box because if I try to transfer to a non-existent or uninitialized VM box, I get the expected "Invalid Mailbox" or "Mailbox not Init".

Any ideas?

One other piece of info, all lines are in HG and do NOT have appearances on any sets. I don't think that it matters because even internal callers experience the same issue, but thought I would add it.

Make sure you have an available I/C path on the phone.

Marv's right (always is). 2 intercom buttons is required to transfer a call using F986. There has to something else your missing?

Yep, there must be something else I am missing. There are almost always 2 I/C paths open on the set even when they are on the phone because there are 3 I/C buttons programmed for each set. Just to be 100% clear I did verify with each test that no other I/C path was in use save for the incoming call. I will put a fresh set of eyes on it tomorrow but as of right now I don't see it.

When calling/trasnferring to a set will it forward to vmail ok?