I am assuming you upgraded from 11.xx to 12.xx? If so, this is most likely going to be due to the change in the timestamp format in the logs. You will likely need to look at the script in the app and figure out what you need to change. What I would likely recommend you consider is getting off the System monitor and utilize the Governance Dashboard app:
This app is fully supported. If you want to continue using the old one, you can look at the script in the GDB app to try to find how we are doing things there and borrow those pieces of scripting...
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