Since you’re able to sign in to your Microsoft account, but the Recovery Key page isn’t loading correctly, this appears to be a server-side issue on Microsoft’s end, especially since multiple users are reporting the same problem when trying to access both the Devices page and the BitLocker Recovery Key page.
At this point, there isn’t anything specific you need to change on your device. I’d recommend waiting for Microsoft to resolve the issue and trying again later.
As a workaround, some users have reported that accessing the Recovery Key page through an InPrivate/Incognito window worked for them: http://aka.ms/myrecoverykey