Visual Studio Solution Unavailable (reload doesn't work)

Question

I am downloading a sample program for a barcode reader that I am using. Everytime I download the program and run it I am prompted with the error in my solution explorer (see ima

Answer 1

I was having the same problem on VS 2017 CE. I opened a .sln and the solution was empty (unavailable).

This solved my problem:

1. open the .sln file in VS
2. right click on the project name (unavailable) in the solution explorer
3. click on "install missing..." (i don't remember the exact text)