Project.dll missing? It was here four hours ago!

I have been working on a project the past few weeks. It was working fine a few hours ago, but when I went to open it a little while ago, it says, {project}.dll is missing. Then asks me to rebuild. I hit yes, and it tells me it failed to rebuild, and then closes. This is a blueprint only project. Anyone know how to fix this?

I tried copying my content into a new project, but then it fails to package for distribution, even though it was also doing that earlier today.

Try Migrating the Project to a Different Version (Newer) & Rebuild. If not… then Reinstall the Unreal Engine Version. That should do the trick.