I've been trying to register for the free credit report service. Tried many times. Fill in all my details and every time I get "this is embarrassing, a technical problem, please try again later." So I have, lots of times and the same error message.
Are you still having problems?
There are other companies that offer free credit reports eg Noodle, Clearscore etc
Alternatively, you could just put your question to the giffgaff Agents https://support2.giffgaff.com/app/ask who I am sure they'll pass it to HQ in order to be given an amswer. Just pick whichever category and cope and paste teh description of your issue from your post on this forum.