I have a process builder that is creating detail records and populating a few fields on creation. I also have an after insert trigger that is firing based on one of the fields that is populated during the record creation in the process builder.  Both function perfectly independently but when a record is created through the process builder that should fire the trigger it does not.  Any ideas or resources would be greatly appreciated since I'm new to triggers?

How do you call a Flow from an Apex class and feed it a record id? Please provide specific example

Is it possible to do a SOQL query that allows me to obtain the SF Id of a master-detail custom field I have in a custom object?  I'm not wanting the ID for a record in the object I want the Id for the actual field.  Field API name is Opportunity__c in a custom object with an API name of Win_Form__c.