About every month, USCIS publishes processing times for its decisions on most USCIS forms. Whenever you receive a receipt notice from USCIS, it should have an address at the bottom of the form (generally on the left side). That is the office that is processing the form. At the top of the form, there is a “receipt” or “priority” date. Check the status of your form by looking at the Processing Times for the office processing your form, checking the published date against your receipt or priority date. If USCIS is processing applications with a date BEFORE your date, then your application should be processed. If not, you can contact USCIS to request that it take action on the case.
See USCIS.gov for Processing times.