Assignment Rules are not running in Production for a Published Model.
The published rules and Territory start date need to be current for a Published Model for the Rules to preview and commit to be sent to Production. An assignment preview does not pick up future-dated rules on a Model which is not currently published (which includes the Planned Publish Date).
Update the Planned Publish Date to a date in the past which the Model should have started committing to Production.
Align Help Documentation: Account Rule Processing.