The 27-year-old singer made the revelation during a visit to "The Ellen DeGeneres Show".
"Sound check was great - went really well. I was really excited and then during the changeover, the microphones fell onto the piano strings which is what the guitar noise was.
"I woke up the next morning to people in England being like, 'We still love you! Don't worry!' And I was like, 'I didn't ask you if you still loved me, but thanks.' I was so embarrassed. I cried pretty much all day," she said.
"Next time I have any sound issues, I am gonna stop. I'll be like, 'Sorry, that's not working for me. If we have time to do it again, let's do it, otherwise, bye!'," she said.