Code coverage is showing 0 % but same code and settings. Earlier it was showing > 0 % value in code coverage in C# .net Framework 4.7.1

Code coverage is showing 0 % but same code and settings earlier it was showing > 0 % value in code coverage in C# .net Framework 4.7.1.
NunitTestEXE - nunit3-console.exe
OpenCoverExe- Opencover.console.exe
WARN: The code coverage report doesn’t contain any coverage data for the included files

NOTE: OpenCover.xml file does not contain main project file, it’s showing only Testproject data.

@Abhishek_Priyadarshy the following two guides would be a good place to start:

  1. the wiki page describing how code is classified as test or product code,

  2. the code coverage troubleshooting guide