I've a couple of flights lined up to the US and so far managed to upgrade one sector on the first flight without any issues.

The second flight though has yet to free up any availability, but what seems strange is that if I try to upgrade with Avios or Cash I get the following error:

'Sorry but we are currently unable to change or cancel your booking online.
Please call 0844 493 0762 to change your booking.'

Any ideas why? Not too concerned as I'm using KVS to monitor availability and I'll phone if anything appears, but just wondered why the error message.

It was booked via TA, but looking at the email receipt they used a credit card to book it online with BA.