bank details correct but appearing as invalid

My first maintennance loan payment was scheduled today and the payment is showing as blocked. I contacted sfe over the phone and re-submit my details verbally despite them saying nothing was flagged on the system however this did not chance the status. today i contacted them through the live chat and was told that it is flagged that my details are invalid, however i have checked them multiple times and they are 100% correct. what could the issue be?