Thank you Gents.
Under ADSL Settings are the following choices:
Multiplex Method...........LLC-Based (ticked)
VC - Based
VPI..............................38
DSL Mode......................ADSL2+ (now ticked)
Auto (multi mode) (was ticked)
ADSL (G.DMT)
Does the router need a reboot after changing from Auto to ADSL2+?
mcdhu