MNOs,

It appears an incompatibility has been found in Sentinel with Dash Core v0.17.0.2 causing it to "report a failure mode" (no exact details available to me at the moment). 

The Core team is on it and creating a sentinel update that will address the issue.

Once the new release is out you will need to update your sentinel with the standard 'git pull' command.

FYI, you can monitor sentinel releases here:
https://github.com/dashpay/sentinel/releases