If this is the case, the only real fix may involve waiting for Roblox's backend systems to resolve the issue. However, you can still contact support and provide them with this additional technical detail to help escalate the issue.

Clear cache and cookies

Sometimes, outdated or corrupted cache and cookies can interfere with account verification processes like PIN input. Clearing your cache and cookies may resolve any lingering issues with session management.

Disable any browser extensions or ad blockers

Sometimes, certain browser extensions or ad blockers interfere with Roblox’s authentication process, preventing you from entering the PIN correctly. Disabling these extensions might allow the PIN verification to go through smoothly.

Contact Roblox support

If the app solution doesn't work, contacting Roblox Support may be necessary. Users have reported success after reaching out to support and asking them to temporarily remove the account PIN.

Roblox Support can manually remove the PIN, allowing you to reattempt adding it afterward. Be sure to mention that you're experiencing the "Unable to authenticate request" error when using a browser.

For most users, switching from the web browser to the Roblox desktop app is the quickest and most effective solution for resolving the "An Unknown Error Occurred" problem when entering a PIN. However, if the issue persists, try clearing your cache, switching browsers, or disabling extensions that may be interfering. Roblox Support is also a helpful resource and can assist with PIN-related issues directly.

By following these steps, you should be able to solve the PIN issue and regain full control over your Roblox account’s security settings.