Unable to receiver incoming calls.

[#1]

Incoming calls drop after one ring although dialling out is fine. I have tried two different phones in the master socket test socket and they work fine, both receiving incoming calls. However, if I leave the line plugged into the test socket then I have no internet access (it's a BT Openreach socket into which both the phone line and router are plugged). I have raised the issue with with Plusnet but have had no response. The phone line belongs to my elderly mother and it is essential we are able to call her, especially during these times. Any ideas?

[#2]

@Lotuslist 

There would have been a filter included with the Hub. If you plug this into the test socket you can connect both your Hub and phone again. 

It sounds like the filtered faceplate might be faulty. You can buy these from the likes of Amazon. Be aware that there are two types, One is held on with two screws whilst the newer ones just clip on. They are not interchangeable 

[#3]

You are experiencing a ring trip, usually caused by a rectified loop somewhere on the line, normally faulty extension wiring or damp/corrosion is the culprit, if you do not have any extensions connected to the master socket then look for any green corrosion on the terminals if you can access them.

[#4]

Thank you so much Baldrick1 - that's exactly what I did after having a 'aha!' moment after posting!