Domain name available when checked, but not on SH

Hello! I am brand new, so forgive me if this is a silly question, but I am hoping someone can shed some light.
I am trying to enter a name that I checked on godaddy and they say the domain name is available, and when trying to check it on SH for the contest, it says it is not available. I have looked at past answers to this, so I tried reloading and going out and back in, to no avail. It is on the contest:
Godaddy does say it is a “premium” name. Any idea what this means or if it could be affecting my name?
Thanks in advance!

I believe that Go Daddy availability means is for purchase as a premium name. Someone owns it and is willing to sell it. SH domain checker will only show domains that are not registered. Hope that helps

Thank you very much for your reply!