You'll probably need to contact 48 support about this.
There seems to have been problems with membership plan purchases lately judging by recent posts here.
However I bought one yesterday and it went through fine so the problem isn't affecting everyone.
To contact 48 support see the links in my signature below.
In the meantime...
What does your My48 account Dashboard say about your current membership plan status, allowance balances and expiry date?
What does your Transactions page say about recent payments/purchases?
