Trying to set up a 007 with delayed call handling.

Programming guide says:
"Each Delayed Call Handling extension (phantom station) must be an unused MFM extension...[and it] must be the principal user of the lines to be handled in the Delayed Call handling mode. Assign a mailbox with COS 15...to the Delayed Call Handling extension."

So, I have an MLX5 in the phone closet, extension 3318, with no MFM. I assigned extension 3408 to the MFM port, and assigned the three lines to be answered.

I then follow the instructions for making 3408 the Principal user. It prompts me for the trunk number (in this case 801, 802 and 805), then prompts for the Delayed Call handling Extension. When I type in 3408 and press enter it just gives me the error beep.

What am I doing wrong?

Other info that might be relevant:

VM ports are in calling group 3400
VM ports are 3401-3406
VM Maintenance port is 3407
VM AA1 DCH Extension should be 3408 (see above)

3408 is in coverage group 5, and set to be covered by calling group 3400

All User extensions are MLX telephones and are numbered 33xx.

Analog ports (one 016 card and a few MFMs) are in the 343x and 344x range..

There are 5 DLCs, 3311, 3312, 3331, 3332 & 3333

Thank you for any assistance you can offer!

Dylan. SATUBAW (Some American techs use BIX as well)!