IPv6 is just the newer addressing and I have not seen any problems using it. I do not know of any sites that are IPv6 only but at some time in the future it will happen. When you do turn it on, use...

Sorry, did not see my post so I re-posted. I suspect the site may have IPv6 only for part of the site. Just a guess on my part. Does your router support IPv6? If so set it up. I had to try several...

ISP is your Internet Service Provider. Things to check. Make sure you have a good Ethernet cable between the modem and router. You can connect your computer via Ethernet cable direct to the modem...

Use a site like https://www.whatismyip.com/ to see if you have both an IPv4 and IPv6 address from your ISP. If so, does your router support IPv6 and if so, set it up to use it.

You are not getting a good signal from your modem or ISP. Note the internet status is "poor network".

Try the 30 30 30 rule https://www.lifewire.com/hard-reset-rule-for-routers-3971318