v 5.13 is way too old one (October 2014) , try a bit new version
Also what is the version of Exchange you are using ?
exchange_monitor probe depends on ntevl probe to fetch and monitor the DAG events for certain profiles, hope you already have it installed?
As mentioned earlier, you should be able to see the Data Availaibility Group displayed under DAG Tab if properly configured, do you see that?
Just out of curiosity do you have the below enabled under Setup tab?
