Hey there! I’ve been working on my project in UE4 for about two weeks now, and have gotten a decent amount of work done. The other night I closed out of UE4, and when I went to open it the next day, I was presented with an error stating
“The following modules are missing or built with a different engine version: UE4Editor-MyProject3.dll. Would you like to rebuild them now?” I click yes, and the build fails, “MyProject3 could not be compiled. Try rebuilding from source manually.” MyProject is using blueprints as the scripting, I created it using the Third Person Template, I did create a new c++ file, just to take a peek at it, my c++ is rusty, but I didn’t add anything to it, just created the file inside of the editor. Is there a way to fix this? I have Visual Studio 2017 installed if I need to somehow open it in it, but the problem is I can’t even open the editor. 
Any help would be greatly appreciated.
Open the .sln file. Build your Project. If it fails Upload the Output Log then we an tell you whats wrong 
if it suceeds congrats you can open your Project again.
There is no .sln file in the project folder, where would it be located?
If you cant generate the .sln file you don´t have all requirements installed. Usuall suspects are Windows 8.1 SDK and .NET. Run your VS Studio installer again (no need to deinstall).
Make sure you have .Net for Desktopdevelopment and Gamedevelopment with C++ checked. https://i.imgur.com/wWY6XMD.png (sry its German)
And as always report any errors you encounter along the way =)
This solved it. I updated Visual Studio, and installed the packages you suggested, along with making sure Windows 8.1 SDK was checked on C++. Afterwards I didn’t even need to generate Visual Studio file, I just stated the project, and had it rebuild there and there was no error this time, I am able to work on my project again! Thanks 