Everybody is having the same problem while roaming in the EU on a Guido membership even though it should work. You'll have to contact 48 support and see if they can do anything for you. By the way you don't have a wifi allowance. You have a network/carrier data allowance. Wifi and carrier data are different things.
Hope this helps.
I am not a 48 employee so if you need to contact 48 support then use option 3 or the chat facility here.