I have this problem too, with both my Huaweis. They work fine in Ireland. I've gone through everything with support. THEY DO NOT HAVE A SOLUTION FOR THIS. So they should be upfront and warn custoers that a Huawei phone does not roam with 48.
Note, I use the same phone outsde Europe and even in Europe with other SIMs without isssue.
My son is in Spain and has no data, is unable to make calls or texts. He on on Guido membership and has extra credit on his account. I have been on to 48 agent 3 times and they said for him to turn on data roaming and change the APN. He has done this and still it is not working. I am having to text his friends phone in order to pass on these messages. Any one have any other tips on how to connect. He has samsung galaxy 8. Thanks
I have roamed abroad on 48 in the past using a Huawei phone so I don't think that that's the problem per se.
I'd suggest that you contact 48 support if you have problems.
See the link in my signature below.
Hope this helps.