What do you mean you haven't received it?
What is your cash credit balance?
Check it on your My 48 account on the website (https://www.48months.ie/my-48) or the app or by dialing *100# and hitting call.
What does your My History page say about recent transactions?
Remember that on 48, unlike other pay as you go networks, cash credit topups and membership purchases are different things.
If you topped up your cash credit balance expecting to get a membership and allowances then you don't and you need to buy membership as a separate step.
Hope this helps.
OK - I see that you (@vincent2000) liked my post here so I presume that it explained your situation too?