I have an old mac book pro that will not turn back on......the line goes halfway and then stops

It would really help to have some more details such as the exact model of the laptop and the OS. You can get the exact model by entering your serial number here:

https://checkcoverage.apple.com/

In the mean time try booting into Safe Mode. It will take a lot longer to boot into Safe Mode because macOS is running a file system check as well as deleting some temp & cache files.

Run the Apple Diagnostics to see if any hardware issues are detected.