I had just purchased and set up a server through Nitrado and the web interface wont allow you to join the server, so I set up my server through Game Tracker and it says my account is to new to claim ownership of a server. Does that matter? Can someone else claim it? Can my account be backdated? Thank you in advance for your help

There is a 7 day waiting period. It is mandatory and immutable.
To be perfectly clear, that is 7 days to the hour from the day/time you joined.

Ensure your server has its 'normal' name during this period (not 'GameTrackerClaimServer') to avoid someone else claiming it.