I've long suspected that the on-going saga of connection type (or multiplexing) setting on your modem is not a client issue but a TCL one.
Basically (one day or several days or even several times in one day) alternate between LLC or Mux-VC settings to get internet connection again.
TCL have told me this is now a 'known issue' and have added my case to others.
They further state that "currently awaiting new line profiles to be added" and "rolled out on 4 exchanges, we are currently testing this"
If you have this problem then place a complaint with TCL.