When you get an error in LoadRunner while replaying or executing the script then an error code and an error message appeared in the log. This error code and error message describe the issue which you need to debug.
But, sometimes it is difficult to understand the actual meaning of error message which leads to search the issue on the internet to find out the resolution. Do you know Micro Focus LoadRunner has a handy error troubleshoot page where all the error messages along with error codes are described? The error codes are listed out in a range so you can select the range under which the error code is falling and then get the error description, cause of error and troubleshooting steps.
I have gathered the troubleshooting page link for LoadRunner 12.56 to 2020_SP3. I would recommend you to bookmark the respective troubleshooting page as per the version of LoadRunner you use and get a quick solution.