smart meter not accepting top ups

I put £20 in at the post office  on Wednesday, as the app never works properly for me, i also put £20 in on Friday when I was away having thought there's no issues with my power when im away. My niece is there, food, gas and electricity all topped up yet no. The meter said top up unsuccessful, I don't know what one as I wasn't here for 2nd top up. Help me find the credit please, Stoo