EDIT:
I've sent in a ticket and they told me how to fix it, and it worked!
- Press Windows + I
- Select Time and Language
- Select Region and Language
- Change your region to United States
- Reboot your PC
Once the game is installed from within the insider hub you can change your settings back as you will no longer need to launch the game from within the insider hub.
I've only just recently joined as an Insider and downloaded the Insider app. Clicking on 'Insider Content', the only available game to join is Minecraft and I can't seem to find the option for Sea of Thieves anywhere.
All the info I could find online is outdated (back during technical alphas). Is this a common problem? Any help would be appreciated!

