I upgraded ISP service from 200/10 to 600/20 Mbps. When I connect laptop directly to Netgear modem I get 610/24 Mbps, but once I connect RT-AC5300 to modem I still get 200 Mbs wired and wireless. Any advice appreciated.
What firmware are you on? What default settings have you changed? What additional features and/or scripts are you using?
When was the last time you performed a full M&M Config? See the link in my signature below for further details on getting your router to a good/known state.