The Konftel 300W doesn't ring
If you have a Konftel 300W connected to a DECT system and it works fine to place a call but when you try to call to the Konftel you don't get the ringing to work. Try the following:

Make sure that you have the latest release (1.6 or higher).

Press MENU once.
Press HOLD for 2 seconds
Press LINE MODE for 2 seconds

A service menu should appear.
Go down to "Ascotel fix" and activate it.

Then restart the phone by removing the battery.