Shell is not the same as a terminal session and likely doesn’t have the environment you expect. You may need to specify the path to your home directory.
I’d start by calling “env” to get a list of environment vars that it does know about and compare the list to what you get when entering env in a terminal window.
Not tested (and it may have typos)… but what about something like this?
Dim results As String
results = DoShellCommand( "osascript -e 'tell application ""Terminal"" to do script ""sh -c /pathoffile/updatescript.sh"" ' " )
This should open Terminal.app and execute your script.