Cannot create account: anti-bot check fails though Turnstile shows Success

Creating a new account fails with "Anti-bot verification failed. Please try again." even though the Cloudflare Turnstile widget on the form shows a green "Success!" checkmark. **Expected:** With Turnstile showing Success, clicking "Create account" should create the account. **Evidence:** The form is fully filled (First name, Last name, Username, Email) and the Turnstile widget shows "Success!". On clicking "Create account", the red error "Anti-bot verification failed. Please try again." appears. In the browser network tab, the POST to `register` returns HTTP 403 with response body: - ok: false - code: "TURNSTILE_FAILED" - message: "Anti-bot verification failed. Please try again." **Where:** Create your account / registration page. **Steps to reproduce:** 1. Go to the registration page 2. Fill in First name, Last name, Username, and Email 3. Wait for the Turnstile widget to show "Success!" 4. Click "Create account" 5. The account is not created; the error "Anti-bot verification failed. Please try again." is shown