I've given out my two invites that I received when I joined the tracker. The first person signed up without issue but the second one didn't try to sign up for a few days and when they tried to do so they weren't able to.
When I look at my invites both have been used and there are 3 accounts listed one is the successful account and the other two are unknown user.

Is it possible to obtain a "refund" on teh second invite seeing as it didn't lead to a successful account creation?

Yes no problems. Your invites where re-added.

Don't forget to remind your invitees that they have 48 hours to register after receiving the invite before it expires!

Thank you, I will indeed.

Hi there, ran into a problem similar as the OP, invited a friend but their invite seems to have died.

Could one of the mods please help to reset this?

I had the same problem at first, then one of the admins gave me the invite back, but when i send it to my friend again, he received the message "Sorry, you are not qualified to be a member of this site".

What does this even mean? How I solve this?

He probably didn't enter all the details correctly when he was trying to register, he might for example not have checked the boxes saying I read the rules etc. Something like that I suspect.

Resend the invite and make sure you explain that they need to register within 48 hours after receiving it!

Thanks! I'll let them know

I don't know if it was that, this happened last year and I lost the invite that day. Can I have the invite back so I can send to him to try again?

The invite was already given back to you! So, yes. Try again!