Haven't worked with welcoming messages / menus (I'm doing minor add/changes to a DK280 which my vendor setup about 10 years ago) so I'm not sure how that recognizes a FAX and sends it to port 008.
A temporary fix might be to use program 81 - "Day Immediate Ring" to turn on ringing for port 008.
Enter program 81, select port 008, and light Button/LED 04. Reminder - on a phone with the standard 4 line desi strip this will be labled Line 3, don't let that confuse you.
