To fix the "Blocked due to unauthorized request (401)" error in Google Search Console, first identify the affected URLs. This error typically occurs when a page requires authentication to access. Ensure that Googlebot is not blocked by authentication settings and allow it access by either removing authentication or whitelisting Googlebots user-agent. Additionally, check your robots.txt file to confirm it isnt blocking access. After resolving the issue, request reindexing through Google Search Console.

For further guidance, read a blog at : https://www.algosaga.com/blog/blocked-due-to-unauthorized-request-401/