The Cascaded Delay looks unusually large. And I see this in the TM ART Central User Guide:
Note If the duration of the cascaded runs exceeds the
execution interval, the skipped monitor execution will
not be executed.
That does not fit what you have exactly but it makes me wonder what would happen if you got rid of the Cascaded Delay.
Thanks for the response, Dan.
The cascaded delay of 590 seconds is the maximum value available and was chosen to space executions as evenly as possible when using a 20 minute interval. At any rate, removing the cascaded delay did not resolve this. ( I have two other projects, out of about fifty, which are showing the monitors with an entry of 'disabled' under the the Next Run column. Neither of the projects uses a cascaded delay.) The non-executing monitors are deployed to a different locations/execution servers and other monitors are running according to schedule on these execution servers.
I'll continue to look at this, if I learn anything I'll add a post.
Again, thanks for the response.
Do you have any blackouts defined? This article indicates that may be a factor: