Referrals shown as ineligible, even though they were using a different network.

Hello, I have a problem with the referral program. I invited two friends who had never used Dropbox to create an account, install Dropbox, and at least one of them still uses Dropbox regularly. They created their accounts from their own homes, so there should be no issue with referrals being blocked due to the same Wi-Fi connection. However, I haven’t received any free space, and I see that both of my referrals are marked as ineligible. How can this be resolved? I’m really interested in Dropbox and am considering a paid plan in the future, but I also wanted to earn some space to start with.