1. Make sure that the handset receiver is off of the hook.
Customer may not know they have to take the handset on and off the hook to use the headset.
(Remember to always check compatibility of phone model and if using an amplifier - compat settings.)
2. If phone has a headset jack and headset is plugged into the jack, look for a HANDSFREE or HEADSET button.
Make sure it's activated. If still no dialtone, try plugging in through the HANDSET jack.
This will determine if their headset jack is activated, or needs programming.(see HDSA #610)
3. The headset may not be connected to the phone correctly.
Sometimes Customers get the cords on the back of the amp or charger base reversed and accidentally plug the Handset into the TEL jack and the black connector cord into the HANDSET jack (the Handset will work in either jack so it is often hard to tell). Have them reverse the cords.
4. See if the power light is coming on when they turn on amp or cordless headset.
If not, have them make sure the batteries are in correctly. If they are in correctly, have them try new batteries.
If they are using a DCA have them unplug it and try the batteries. If a power light still will not come on then the amp should probably be replaced.
6. Make sure the cords are fully plugged in.
Double check all of the connections. Also make sure that they are using the connector cord that came with the unit.