Error recreating a sub-account in SAP Cloud Platform Trial

I'm currently doing the Open SAP S4 HANA SDK course. After some initial success I ended up with a some code that wasn't working, so I decided to start again with a clean sheet.and deleted the sub account I had created. I now cannot create the sub account with the same name as before even though it does not appear to exist in the account sub-accounts:

I can create a new sub-account with a new name but there is no quota left to assign to it (i.e. no memory, service etc.).

It looks like the original 'Dev' sub account is in a zombie state but I can't find anyway to kill it properly and get the quota back.

Has anybody any ideas?

Thanks,

Dave