I have a landline (non VOIP) issue where I get no incoming ring in hot weather, although an incoming call can be answered fine even though the bells are silent, outgoing calls OK. The phone ringer is testing ok on a BT landline. Use of an inductive amplifier you can hear an attempt to send ringing current from your netwiork to my phone heard at the incoming socket and all other sockets, but your power levels in the cabinet are insufficient to activate the bells in hot weather. Cool weather and all works fine!
VM on twitter people gave me a VM text number. The people on that text number tested it and arranged for an engineer, saying the 'technician will be with you on the 17/08/2020 between 12 and 4 o'clock'. No one came! You cant get through on the phone to anyone at VM 151 and they refuse to answer the texts for me to know what happened, if anything? VM on twitter said to contact a moderator here as I am now in a position where I might miss urgent calls if the sun is out.