There are lot of common errors that we keep encountering while using Loadrunner, like HTTP status code 401, 500, 403 etc.
If you encounter error HTTP Status Code 401 Unauthorized, during HTTP/HTML script replay then try below options:
Option 1: Add web_set_user(username,password,host:port );
Option 2: Record the script after changing the capture level to Wininet level data in Recording option> Network > Port mapping > capture level
Option 3: Run the script after enabling Wininet replay instead of sockets option in Run time settings > Internet Protocol > Preferences> Advanced
Option 4 : If none of the above option works, record the business flow with fiddler and compare the requests in LoadRunner and fiddler. Identify if any request/header/cookie is missing in the load runner script and causing the issue.