Looks as though a couple of PSTN tests have been done by support. Both entries are showing this or similar wording.
WLR3Test WLR3_CIDT_Test hws00556dat02:133362221: Fail Fault - No Dial tone(Line Test OK) ServiceLevel:1, MainFaultLocation:EX, FaultReportAdvised:Y, AppointmentRequired:N, LineStability:, NetworkStability:, StabilityStatement:
Edit: If mods wish, I could start a new thread as this isn’t strictly related to the thread title.
Edit 2: So, I'm feeling a bit stupid. Had an email from support asking to try another router, which I did, a Asus. This connected fine. I've since factory defaulted the Pfsense router and restored a config and this is now also connecting ok. I'm not sure why it's suddenly started to drop the connection though. Hopefully be ok now.