What else can I do to solve the problems with the L4D file?

The reasons for the lack of the ability to open a L4D file on your computer may be at least several. The easiest thing is to find a suitable application installed on your computer, which will open a L4D file. If there is still something wrong, you might want to check:

.L4D file extension
  • whether the L4D file is not damaged
  • whether the file is not incorrectly linked in the registry entries
  • whether the installation of an application that supports the given file format is complete
  • whether the file is not infected
  • whether the drivers of the equipment used for opening a file are up to date
  • whether your computer has enough parameter/hardware resources to open a file with the given extension
  • whether the extension has not been accidentally removed from the Windows registry

Is the L4D file still not working with your software after eliminating the above shortcomings? That means that the problem is more complex and requires the help of a specialist.