Not sure how to fix this issue but on my computer I have my Epic Game Launcher installed and also have the latest version of UE4 installed. I logged out of the launcher and my son logged in using his account so he could install and play a game that is in his library. When he was done and logged out and I logged back in, I found that my UE4 told me that it was not installed.
I found a solution on how to fix it by starting a new install, cancel it and rename folders and do some cleanup of temp files and then resume to make the installer see that the files already exist and then it does a verify. That all worked and I’m back with UE4 installed. Now every time I log out of my computer, shut the computer down, or even log out of the launcher and log back in, I’m greeted with the message that UE4 is not installed again. I repeat the process and it works until the next time I turn on my computer. I have did this process many times and it never seems to think its installed.
The UE4 icon that is placed on the desktop works with the Game Launcher still thinking its not installed. If I create a project using UE4 using desktop icon, The launcher does not see my new project until I fix the launcher issue,
I contacted Epic Games and they gave me instructions to remove the webcache folder in the %localappdata%/Epic Games Launch directory. That did not fix the issue. I even reinstalled EGL to a different hard drive and the issue continues.