Hello, Clive.
It's disappointing to hear your code wasn't working. Reopening the Three+ app would be unlikely to resolve the issue since you already have the code, the Three+ app has done it's part at that point and would only be able to re-issue the same code.
The codes you get through Three+ are generated by the companies that Three have partnered with, in this case Café Nero. In order to get advice on why the code hasn't worked, or why it's showing as used when it hasn't been used, you would probably need to contact their customer support team to ask them there.
Pete.
Mod tip! The author of a post can hit 'Accept as Solution', to highlight a reply that helped solved their query.
