Custom Metadata types not supported in Apex Classes?

Question

I'm using a Custom Metadata type to hold the counter for a round robin. The following code provokes an error:

Account_Managers_List__mdt AMList = Account_Managers_List__mdt.getInstance('m0717000000DDIYAA4');

Which causes this error: DealTrigger: execution of BeforeUpdate caused by: System.TypeException: Unsupported sobject type and/or version Class.DealTriggerHandler.beforeUpdate: line 57, column 1 Class.TriggerFactory.execute: line 46, column 1

Any thoughts on what's causing Unsupported Sobject type? When I put this line in execute Async it works fine. in fact, the whole counter works perfect in execute Async, but when I update the deal object it returns this error.

This is the DealTrigger

 public void beforeUpdate()
{
    System.debug('In am in beforeUpdate'+DealTriggerHandler.firstRun);
    Map<Id, Deal__c> oldMap = (Map<Id, Deal__c>)trigger.oldMap;
    Map<Id, Deal__c> newMap = (Map<Id, Deal__c>)trigger.newMap;
    
    for(Deal__c deal : (List<Deal__c>)Trigger.New) {
        
        //if(deal.StageName__c == 'Contracts Approved') {
        if((oldMap.get(deal.Id).StageName__c != newMap.get(deal.Id).StageName__c)
            && newMap.get(deal.Id).StageName__c == 'Contracts Approved'
            && oldMap.get(deal.Id).Contracts_Approved_Date__c == null) {
            
                deal.Contracts_Approved_Date__c = System.today();
                    
                //Begin Intro Closing Call Agent Assignment Counter
             
                //Get count from Custom Settings
                IntroClosingCallAgentAssignCounter__c AssignmentCount = IntroClosingCallAgentAssignCounter__c.getOrgDefaults();
                integer Count = Math.round(AssignmentCount.CounterNumber__c);
                
                //Get list of Account Managers

                Account_Managers_List__mdt AMList = Account_Managers_List__mdt.getInstance('m0717000000DDIYAA4');
                
                //Serialize and map a copy to work from
                String str = JSON.serialize(AMList);
                Map<String, Object> AMObjMap = (Map<String,Object>)JSON.deserializeUntyped(str);
                
                //Remove fluff
                AMObjMap.remove('DeveloperName'); 
                AMObjMap.remove('Id');
                AMObjMap.remove('Label');
                AMObjMap.remove('Language');
                AMObjMap.remove('MasterLabel');
                AMObjMap.remove('NamespacePrefix');
                AMObjMap.remove('attributes');
                AMObjMap.remove('QualifiedApiName');
                
                //Get a list from the remaining values
                List<Object> AccountManagers = AMOBjMap.values();
                
                //Take the Modulus and round it
                integer RefModulus = Math.round(Math.mod(Count, AccountManagers.size()));
                
                //Get the account manager as an Id
                Id i = Id.valueOf(JSON.serialize(AccountManagers[RefModulus]).replaceAll('"',''));
                
                //Increment
                AssignmentCount.CounterNumber__c=Count+1;
                
                //Assign
                deal.Intro_Closing_Call_Agent__c = i;
                
                //Update Counter
                update AssignmentCount;
        }
        
        else if((oldMap.get(deal.Id).StageName__c != newMap.get(deal.Id).StageName__c)
            && newMap.get(deal.Id).StageName__c == 'Contracts Approved') {
            
            deal.Last_Contracts_Approved_Date__c = System.now();
        }
        
    }
}

this is the factory

public static void createHandler(Type t)
{
    // Get a handler appropriate to the object being processed
    ITrigger handler = getHandler(t);
     
    // Make sure we have a handler registered, new handlers must be registered in the getHandler method.
    if (handler == null)
    {
        throw new TriggerException('No Trigger Handler found named: ' + t.getName());
    }
     
    // Execute the handler to fulfil the trigger
    execute(handler);
}

Answer 1

getInstance method is a new addition that is supported on api version v51 and upwards. You need to update your DealTriggerHandler class api version to 51.

Here is the relevant documentation