Generate a transcript and also add statements to log start and stop times.
Start-Transcript -Path C:\Scripts\Logs\MyScript.log
"$(get-date) - Script is starting."
# put the rest of your script here
"$(get-date) - Script is ending."
Stop-Transcript
Add additional statements in your script at key points in the processing. If you are accessing folders or shares, add in Test-Path or Get-Childitem statements to verify that your script can see the files that it needs to process. Review the MyScript.log file to see what it did.