Fully aware there are other threads up here on this, but maybe if there are more, Tesco will actually do something about it...

Have been trying to pay off my balance for about 2 weeks now online with my debit card (as normal) - error every single time. Clearly there is an issue with the system as its affecting quite a lot of people.

If it continues, it might be time to switch to a different CC. Not convenient at all.