In version 10.6 and above when creating a Custom Trigger you will need to paste a .txt file in the Executor path as shown below instead of entering the scripts name there.
To create a txt file you need to path to => ManageEngine\Service Desk\integrations\Custom scripts\Executor_file.
You need to create a new txt file and paste the "py CreateJiraTicket.py $COMPLETE_V3_JSON_FILE" in that txt file.
While doing this if you get an error saying "Can't find a default Python" in the history ! You need to follow the below mentioned solution.
Instead of "py" in the txt file ("py CreateJiraTicket.py $COMPLETE_V3_JSON_FILE" ) you need to enter the complete path of the python installation.
For Example: C:\Users\AppData\Local\Programs\Python\Python310\python.exe send_mail.py $COMPLETE_V3_JSON_FILE.