Your post was blank @JackB2594 and the subject line doesn't really contain enough information to adequately explain your issue/question.
If you want assistance from the Community Forum then you need to explain/describe your issue question clearly.
When was everything, including mobile data, working ok for you last?
What happened in the meantime?
What exactly do your mean by "top up" here?
Since there's no membership plan that costs €20 I presume that you added €20 cash credit to your account?
Cash credit alone doesn't give you mobile data or access to any other outgoing services.
For that you need to buy a monthly membership plan.
See here:
As well as an active monthly membership plan you also need your APN settings configured correctly for mobile data to work.
If you've just joined 48 then you might want to read the New To 48 FAQs to understand how 48 works because it's a little different to some other SIM only pay as you go mobile services.
If that doesn't help then you'll need to provide more detailed information about your issue/question.
If you need to contact 48 support about this then see the links in my signature below.
