Luke, the IP7XX phones require a line key to be available for every active call, so in a transfer operation, you must have at least 2 keys for that line on the phone. Below is an example of the portion of a working configuration showing the button setup:
# This is the line definition. Reg.x.TEXT where x is the line number that will
# be used to reference this line to a line button
Reg.0.DisplayName John Doe
# Buttons are numbered from 1 to 4. Button.n.Label defines the text
# that will be displayed on the LCD next to each button.
Thanks for the info Jay. I managed to get this working a while ago by doing just what you said here. I will still copy down these notes and save them for future use.
I went ahead and flagged the "Correct Answer" on this post to make it more visible and help other members of the community find solutions more easily. If you don't feel like the answer I marked was correct, feel free to come back to this post to unmark it and select another in its place with the applicable buttons. If you have any additional information on this that others may benefit from, please come back to this post to provide an update. If you still need assistance, we would be more than happy to continue working with you on this - just let us know in a reply.