No cash credits earned for signing up via friend referral

I entered the friend invitation code, but it kept saying it was invalid. I exited to start over, but it turns out I was already signed up without an invitation.

I entered the code correctly several times, but it seems like a site error, so I couldn't receive the cash reward.

Please make corrections to earn cash.

There has been a site error since yesterday.

Invitation code HRZV5NMC