I have been unable to upgrade to 2018.

I have not seen that error, but from experience the error that causes the install to fail is not always the last line. It is usually somewhere up in the log and does not necessarily have an error message in it.

I would look into the prereqs and make sure all the C++ redistributables and other things are installing. Then retry the installation and see what happens.

Use the Find command and look for 'return value 3'

Details on where the install failed will be directly above this line.