I had an quite unusual case of this error, but maybe someone would benefit from it.
I had this error with missing .dll file of one of projects in solution (with target framework netstandard 2.0) I'm working on and at once error with reference (to Microsoft.Office.Interop.Word) this project uses.
This solution was cloned from git repository, and same solution compiled well for other people in my team.
I tried every propsed solution for issue - restarting VS, computer; cleaning project; checking and unchecking build checkboxes; checking if build order is proper etc.
I figured out that manifest of this project was not selected by default (dropdown of manifest in project properties was empty and disabled). Therefore I tried to add it, but nothing worked.
At last I started comparing this project .csproj file with one in other, older version of this project, which compiled without problem. After a bit of usless tries I figured out, that path to Microsoft.Office.Interop.Word is the same in both projects, even thought it was a relative path starting with lots of "go up" symbols ( ..\ ). And not working project was one level lower than other.
Adding one more "go up" symbol ( ..\ ) in reference path to Microsoft.Office.Interop.Word inside project .csproj file solved the issue.
I have no idea why this path was created that way and doesn't update in my case, while it work properly for others in my team.