I'm a bit confused here on how to get an invite to the Preview Group....

You have to be invited, which allows you to download the Preview App, it has surveys, quests and info on updates etc. You can also un-register from the program under the registration section, but you have to be invited first. I am not 100% sure but assume
you can register again if you un-registered.

The Next Gen Version of GTA 5 is available with Online as a standalone product. Story mode should be able to be installed from the management page for that app if you purchased the full package

Oh I got Grand theft auto 5 online and story I got worried a bit ty

Hello, KingLonmc. I'm Arturo, a community user like you, and I'll be glad to provide assistance with your inquiry today.

Is the edition below the one you purchased?
https://www.xbox.com/games/store/grand-theft-auto-v-xbox-series-x-s/9nxmbtb02zsf

If your answer is affirmative, it's normal to receive GTA Online because to access the Story mode, GTA Online is required as mentioned in the story mode description.
https://www.xbox.com/games/store/grand-theft-auto-v-story-mode-xbox-series-xs/9PCCGHDBMR1P/0010 > “Requires access to Grand Theft Auto Online for Xbox Series X|S.”

So, once the console downloads GTA Online, and if you purchased the bundle I shared above, you should be able to access to the Story mode.

I'll remain attentive to any other inquiry you may have.

Regards,

Arturo.

I have group not found as well. The faq on xbox says to go to the preview forums if your invite message was deleted. I'm chasing my tail here lol