Hi Steven, the issue seems to be your test class.
I expected to see a Lookup or Master Detail field called Zuora__Account__c linking Zuora__SubscriptionRatePlan__c  to the Account.
See updated test class below

@isTest
private class RatePlanDeletionTest {
	
	@isTest static void test_method_one() {
		// Create Account and Contact 
		Account acc = New Account();
		acc.Name = '1234567890987654321';
		acc.Local_Listings__c = true;

		insert acc;

		Contact myCon = New Contact();
		myCon.FirstName = 'Steve';
		myCon.LastName  = 'Welderbeast';
		myCon.Email     = 'apextest@gmail.com';
		myCon.AccountId = acc.Id;

		insert myCon;
	
		// Create Subscription
		Zuora__Subscription__c mySub = New Zuora__Subscription__c();
		mySub.Name = 'Apex Test Sub';
		mySub.Zuora__Zuora_Id__c = '1';
	
		insert mySub;

		// Local Listings
		Zuora__SubscriptionRatePlan__c myRateLL = New Zuora__SubscriptionRatePlan__c();
		myRateLL.Zuora__Subscription__c = mySub.Id;
		myRateLL.Name = 'Local Listings';
        myRateLL.Zuora__Account__c  = acc.Id;

		insert myRateLL;
		delete myRateLL;

		Account accLL = [SELECT Local_Listings__c
						   FROM Account
						  WHERE Id = :acc.Id];

		system.assertEquals(false,accLL.Local_Listings__c);

		// Engage 
		Zuora__SubscriptionRatePlan__c myRateE = New Zuora__SubscriptionRatePlan__c();
		myRateE.Zuora__Subscription__c = mySub.Id;
		myRateE.Name = 'Engage';
        myRateE.Zuora__Account__c = acc.Id;

		insert myRateE;
		delete myRateE;

		Account accE = [SELECT Engage__c
						   FROM Account
						  WHERE Id = :acc.Id];

		system.assertEquals(false,accE.Engage__c);

		// Reviews
		Zuora__SubscriptionRatePlan__c myRateR = New Zuora__SubscriptionRatePlan__c();
		myRateR.Zuora__Subscription__c = mySub.Id;
		myRateR.Name = 'Review';
        myRateR.Zuora__Account__c = acc.Id;

		insert myRateR;
		delete myRateR;

		Account accR = [SELECT Reviews__c
						   FROM Account
						  WHERE Id = :acc.Id];

		system.assertEquals(false,accR.Reviews__c);

		// SEO
		Zuora__SubscriptionRatePlan__c myRateSEO = New Zuora__SubscriptionRatePlan__c();
		myRateSEO.Zuora__Subscription__c = mySub.Id;
		myRateSEO.Name = 'SEO';
        myRateSEO.Zuora__Account__c = acc.Id;

		insert myRateSEO;
		delete myRateSEO;

		Account accSEO = [SELECT SEO__c
						    FROM Account
						   WHERE Id = :acc.Id];

		system.assertEquals(false,accSEO.SEO__c);

		// Social Ads
		Zuora__SubscriptionRatePlan__c myRateSA = New Zuora__SubscriptionRatePlan__c();
		myRateSA.Zuora__Subscription__c = mySub.Id;
		myRateSA.Name = 'Social Ads';
        myRateSA.Zuora__Account__c = acc.Id;

		insert myRateSA;
		delete myRateSA;

		Account accSA = [SELECT Social_Ads__c
						   FROM Account
						  WHERE Id = :acc.Id];

		system.assertEquals(false,accSA.Social_Ads__c);

		// Social Posting
		Zuora__SubscriptionRatePlan__c myRateSP = New Zuora__SubscriptionRatePlan__c();
		myRateSP.Zuora__Subscription__c = mySub.Id;
		myRateSP.Name = 'Social Posting';
        myRateSP.Zuora__Account__c = acc.Id;

		insert myRateSP;
		delete myRateSP;

		Account accSP = [SELECT Social_Posting__c
						   FROM Account
						  WHERE Id = :acc.Id];

		system.assertEquals(false,accSP.Social_Posting__c);

		// Website
		Zuora__SubscriptionRatePlan__c myRateW = New Zuora__SubscriptionRatePlan__c();
		myRateW.Zuora__Subscription__c = mySub.Id;
		myRateW.Name = 'Social Posting';
        myRateW.Zuora__Account__c = acc.Id;

		insert myRateW;
		delete myRateW;

		Account accW = [SELECT Website_Product__c
						   FROM Account
						  WHERE Id = :acc.Id];

		system.assertEquals(false,accW.Website_Product__c);

	}

		
}