I have confirmed that AI Studio works on my personal Linux Laptop with Firefox. When signing in to my windows work laptop on edge with my Google account (18+, address in the US) I get redirected to this page: Available regions for Google AI Studio and Gemini API | Google AI for Developers. AI Studio worked fine until I mistakenly cleared cookies of my Google account and signed back in earlier this week on my work laptop.
Edit: I signed in to my other account that was not age verified first, so then it was set as my default. Signing out of all accounts and then signing in to my primary account first fixed the issue.