Nonename

Hi, I've applied for a fixed rate cash ISA account on 4 April 2024 and put 20000 into it. But I realized the remaining allowance was still 20000 on 8 April and I put additional 20000 into it again. However when i tried to withdraw the previous 20000 then failed. It seems I couldn't transfer money from that account at all. Could I have any advice about what i should do afterwards? Thanks in advance.