Need Help!

I got invited to the Skate Playtest for 11th March at 1400. 

When I went to approve it, I went to put my gamertag in, and then it said it timed out or whatever it was. I've recently removed/unlinked my old gamertag and linked my current gamertag that I use all the time to my EA account. 

So now I'm frustrated that possibly it'll get sent to my old gamertag?

Can someone explain how this works?

Would I still be able to play?

If I could get some clarification, that'd be great. 

Thanks!