Trigger change ownership of case from Q to User after Turning off Case Assignment Rule

Question

I'm using LiveHelpNow to create Cases and it works fine, I do capture the LiveHelpNow Agent name/SF user Name to a custom field Case.Case_owner__c. However I run a loop to compare it to User object and match it against existing users in SF User Object. Also I check if the case was assigned to Queue I need my Trigger to run after the case got assigned to the queue and replace the Queue owner to the user name I captured and matched with the salesforce user name. code is not giving any error but no Case is being creating. Any Idea?

Note: Im using DmlOption to turn off the case assignment rule for cases only coming for LiveHelpNow.

trigger LiveHelpAfterInsert on Case (after update){
    Map<String, Id> cases = new Map<String, Id>();
    Set<String> ownerName = new Set<String>();
    for(Case record: Trigger.new)
    {
        if(String.ValueOf(record.OwnerId).startsWith('00G'))
        {
            cases.put(record.Case_owner__c, null);
            ownerName.add(record.Case_owner__c);
        }
    }
    for(User record:[select Id, Name from User where Name IN:cases.keySet()])
    {
        cases.put(record.Name, record.Id);
    }
    Database.DMLOptions options = new Database.DMLOptions();  
    options.AssignmentRuleHeader.useDefaultRule = false; 
    for(Case record : Trigger.new)
    { 
        record.setOptions(options);
        record.OwnerId = cases.get(record.Case_owner__c);           
    } 
}

Answer 1

You need to run your trigger on AfterUpdate, NOT as an AfterInsert trigger if your Cases are being assigned to a Queue via an Assignment Rule. AfterInsert triggers execute immediately before Assignment Rules fire. So at the point in the execution context where the trigger you've written above executes, any new Case records that are created wouldn't have been assigned to a Queue for your current trigger to find them and reassign them to new owners.

Presumably there would be workflow that occurs on Case that would cause an AfterUpdate trigger to run in the same execution context which would allow your trigger to perform the reassignment. If not, you'll need to create some.

See Triggers and Order of Execution.