reasonForNotRouting will be returned only if the Omni-Channel Flow didn’t invoke Route Work action.

Message set to the reasonForNotRouting variable in the Omni-Channel flow will be shown on the Messaging Chat Widget.

Sample Omni-Channel Flow:

Sample Apex Class:

public class BusinessHoursController {
    
    @InvocableMethod( label='Business Hours Check' )
    public static List < BusinessHoursOutput > checkBusinessHours(
        List < String > listRecordIds
    ) {
        
        if ( 
            listRecordIds != null &&
            listRecordIds.size() > 0 
        ) {
            
            System.debug(
                'Record Id::' +
                listRecordIds.get( 0 )
            );
            
        }
        
        BusinessHoursOutput objOutput = new BusinessHoursOutput();
        
        // Get the business hours
        Id BHId = [
            SELECT Id 
            FROM BusinessHours 
            WHERE Name = 'Default' 
            LIMIT 1
        ].Id;
        
        // Current date and time
        Datetime now = System.now();
        System.debug( 'now::' + now );
        
        // Check if fall within business hours
        Boolean isWithinBH = BusinessHours.isWithin(
            BHId, now
        );
        System.debug( isWithinBH );
        
        if ( !isWithinBH ) {
            
            objOutput.strMessage
                = 'I cannot transfer now. ' +
                'It is outside of Business Hours. ' +
                'For emergency, call our 24/7 1800';
            
        }
        
        objOutput.isWithinBusinessHours = isWithinBH;
        return new List < BusinessHoursOutput > { objOutput };
        
    }
    
    public class BusinessHoursOutput {
        
        @InvocableVariable( required=true )
        public String strMessage;
        @InvocableVariable( required=true )
        public Boolean isWithinBusinessHours;
            
    }
    
}

Business Hours Check Configuration:

Is within Business Hours? Flow Decision Configuration:

Route to Messaging Queue Route Work Configuration:

Reason for Not Routing Assignment Configuration:

Output: