error message when i try to get to the app


hi, I was travelling the last two weeks in Asia and I needed to top up my account. I managed that successfully when I was in Vietnam, but when i went to Cambodia and tried to get to the app and see my remaining balance I couldn’t. i was asked to provide my phone, which I did and I was sent a text with a code, which I typed to the requested page. But again I wasnt allowed in my account and got an error message that something went wrong please try again later. I am now back in the UK, but still get the same error when i try to get to the app. can someone please advise what i have to do?