Today I tried submitting form for access to D1 Closed beta. After the first submission, there was not any confirmation (email or popup on site), so I tried a second time with dev tool and it showed an HTTP 400 error response with empty body:
"error": "{}"
}```
Key "cookie" value in POST body was null
Errors in console:

Screenshots are from the last try in incognito mode with dummy data to test if it was happening because of the already used email.