Problem with CT11 cordless handsets

[Tripoth]

Partner ACS release 7.
I have 5 of these cordless sets. They are plugged into the aux port on the back of Eurostyle 18Ds.
Sometimes when the clients are wandering around, they hear their phone ring, but not the cordless set. The cordless set cannot pick up the call either. The client has to head back to their phone and pick up the call manually on the handset.
Has anyone run into this issue? Is there a fix? Is there a problem with the units? This is the first time that I am using them.

 

[HyTech]

1) When the phone is in the standby mode,
press MENU/MUTE.
2) Press up or down to
move the pointer
to “Ringer Volume”,
then press SELECT/CH.
3) Press up or down to move the pointer
through the ringer settings (Ringer Off,
Ringer Low, or
Ringer High).
You will hear a
ringer or melody
at the selected volume (or does not ring
when you select “Ringer Off”).
4) Press SELECT/CH, and you will hear
a confirmation tone.
5) Press END to exit.

 

[Tripoth]

So you are thinking that they are turning their ringing off?
I will check, but it only happens sometimes. They will miss a call and then the next one rings on the set.
It happens with all the units as well.

 

[HyTech]

I would hope by default, that it would ring. I would even try using a splitter on the jack instead of using the aux port.