Now resolved. Dante labs gave her an 8 digit instead of 7 digit code. She took out one zero and it has worked. What a shambles of a company she was almost about to buy a second set of tests elsewhere. Now have zero confidence in her getting any results from these test.
@DanteLabs Please help urgently. My mum is on the Eurostar and her Dyy 2 and 8 PCR unique reference is not accepted by the UK gov passenger locator form!! She will not be allowed in without this form completed. She paid for an received the test. Why is the reference not working??