Does anybody know when there which scenario you would get the on another call message

When you try to intercom that person and "he/she is "On another call"

That's what I thought
But I was on the phone testing with the customer today and it won't show when you call them and they are in another call.
Yet some phones apparently do.
Don't know what to make of that...
Any thoughts?

To test, make sure you are on an actual call - not just the intercom - but a line.

Then when you call, it will show something else at first then after 2-4 seconds it will change over to "On Another Call".
Did you wait long enough ???

How many IC keys do the phones have that are reporting this???

Not sure how long they waited
I'll have them let or ring longer.

They have 2 intercoms and also tried with 1 intercom

Just tested with the customer, customer made a phone call connected and was online while someone else called them and the phone rang at least four times and he still did not get the message

Which phone system?
What software level?
What phone model?

MICS
Software is 6 or 7.? I honestly don't remember but it's not that old
T7316e phones

Is there another set/sets that has an Answer DN for that problem phone?

Do they have an Internal Auto Dial on the row of 16 keys for the phone they are trying to call?

No answer DNs
But I do remember they had said they DID NOT have an appearance of the phone in question on a button on the add on module.

Do you think they need to appear on the add on?