when I wrote I want to apologise it was not accepted and the correct answer given was "can you excuse me" so next time I wrote "can you excuse me" and the correct translation given was I want to apoligise. No matter which answer I use it is wrong every time. What's going on here.
The American and Canadian English spelling of the word apologize/apologise is "apologize." I suspect that Duolingo is not accepting "apologise" which is the British English spelling of the word. According to Grammarist, the original spelling in Britain was "apologize." See Grammarist at https://grammarist.com/spelling/apologise-apologize/