Wifi Slow and Modem "Offline"

I pay for 1gb internet, yet our speeds have been abysmal these past few days. Download speed is practically nothing and upload speed maxes out at 25 mbps. Additionally, the xfinity app keeps considering our modem (an arris Surfboard sb6190) as "offline" even though it isn't. I can connect to wifi just fine, it's just incredibly slow.