I'm an F2B category. Original PD of Nov/2013. My i-485 PD is 9/6/2018 and like you my interview was cancelled on 10/22/2018. I've spoken to USCIS twice since then. The one person I talked to last week explained to me that they will remove you from the interview queue if they are not ready for you (I'm assuming because I applied through date for filling and not final action date). She said that once they review all the documents and are prepared for me, they'd add me back on the interview queue. She also said this wouldn't affect the approval of my EAD/AP so I wouldn't worry too much.
Hope that helps!
julesriccio got a reaction from beachlover in Interview Cancelled by USCIS