Videophone video quality troubleshooting as following. Always start the easiest and most common cause of the problem. This applies with can't making outgoing calls, no calls can be revived and other issues. I'm focus on most common issues here.
First, inspect ALL Ethernet connectors, Physical ports, Ethernet cable itself make sure there is no loosen, damaged of frayed. Why check that part first? It is because Ethernet itself moves and gets interference the most and gets broken easily, thus cheapest n easiest to fix. Often I get customers in the past complaining about video only to find out that their Ethernet connector were half way connected and solved the problem after fully plugged in. Other time, some customers found animals chewing the Ethernet, causing video quality to degraded. Having Ethernet cable running below the doorway is a NO NO NO, under rug is a NO NO NO. Ethernet has 4 pairs of thin wires in it, total of 8 wires in it and they are very thin. The thinner it is, the easier for it to break.
If found nothing wrong with Ethernet, then turn power off on everything that has to do with Internet, including VP, Router, switch, modem, whatever. Turn all of them off and let them cool down at lest 5 minutes. Turn back on, and if there is still issue with Video, call ISP to have outside drop line checked. Call ISP *FIRST* to see if they got issues with the Internet. Do not tell them that you are having issues with Videophone, they know NOTHING and will refer you to VRS companies instead. Just explain to ISP that you are noticing issues with Internet connections and have them check it out.
If fails, call your default VRS provider technical support for any other troubleshooting steps. There are various steps to take, depending on what the problem is. My recommendation really applies to ALL VRS customers that calling VRS technical support for assistance is really the last thing you want to call, not first.
And here is number one myth that I hear pretty much everyday for years that getting faster router will increase ISP speed and improve the video. That is FALSE. Most routers today are already exceeding the speed that ISP provides. Only defective routers may cause problem,.