Incremental transfer gray on Appflow from Google Analytics4 to Amazon RDS for PostgreSQL

I created flows from Google Analytics4 to Amazon RDS for PostgreSQL, after a couple of days the incremental transfer option under 'Flow trigger' -> 'Run flow on schedule' became gray.

The existing flows are still running as scheduled, but I cannot edit the schedule or create a new flow to run incremental transfers on schedule because the option is gray as shown in the screenshot.

Is there a reason this happened. I can create new flows and run on demand, but running on schedule is just not working.