Validation Rule: Picklist Field Required - Based on Lookup Field Values Selected First

Question

I have users searching for values in a Lookup field in Salesforce on a Custom Object. When these users select 8 specific values (out of the long list) I want to have a subsequent picklist (File_Type__c) required to be populated with a value.

The validation rule I have created below is not working. What am I missing here?

AND(    
Primary_Application__c = "B2B - Supply Chain - 3PLs",     
Primary_Application__c = "B2B - Banks - JP Morgan Chase",     
Primary_Application__c = "B2B - Banks - Wells Fargo",     
Primary_Application__c = "B2B - Banks - Bank of America",     
Primary_Application__c = "B2B - Banks - Other",   
Primary_Application__c = "B2B - Banks - SVB",     
Primary_Application__c = "B2B - Supply Chain - Retailers",    
Primary_Application__c = "B2B - Supply Chain - Suppliers",    
(ISPICKVAL(File_Type__c," ")) 
)

Answer 1

Lookup fields don't have a string value like "B2B - Banks - Other"; their literal content is the Salesforce Ids of the objects to which they're linked. You can access values on the other side of the relationship, on the linked-to object, with relationship notation:

Primary_Application__r.Name = "B2B - Supply Chain - 3PLs",

I'm assuming that the value you want lives in the Name field on the object you're looking up to; if not, adjust the above to use the API name of the relevant field.