Go to the TP Link web site and check the current level of firmware for your router. https://www.tp-link.com/us/support/download/archer-c9/v4/ This is for the version 4 (V4). Your version level will be printed on the router. Since every thing was working and then you had issues I would suspect the ISP, modem, or your wiring. Try a different Ethernet cable between the modem and router. Another test is to bypass the router and connect a PC direct to the modem and see if all works fine. If not, it could be the modem, your wiring or connectors or the ISP. Check the modem logs. Did you change anything to do with Spectrum such as add, change, or remove a TV as that may be the cause?