I applied with you guys for the I-751 Removal of Conditions, and I received the I-797 notice of action a month ago. I haven't heard anything so what's the next step?
As of 2019, you could probably expect delays and you may not hear anything for five to six months. The normal processing time to remove conditions is usually about six to eight months. After you receive your notice of action, you may in fact receive a letter requesting an interview, however, not all applicants receive that. But you could expect that in about two to three months. If that doesn't come, you can always check your case status online to see if any RFEs, Requests For Evidence, has been issued or if there is any correspondence.
You could also contact the USCIS. You should see the phone number on the notice of action letter that you received. It'll also have the address of the processing center but you can contact them if you don't hear anything for a delayed period of time. If you don't have this, try calling the main USCIS line at 1 (800) 375-5283.