#2 Mar 25, 2017 20:49
The 503 error "System upgrade is in progress. " is normal at this point.
The 500 error "green screen" you screenshoted is complete BS from your webhosting company. If the script "requested isn't found at this location", they should send back a 404 message and not a 500 error.
1) So, first, you need to go and check if
install/index.php actually exists on your server at the time that error is displayed.
2) Then, if it exists, you need to look at the apache error log to see exactly what error is recorded at the time you get the green screen above.