Try this first.
Open a command prompt (Right click and "run as Adminstrator")
Type this, and then press ENTER:
netsh int tcp set global autotuninglevel=disabled
If it says Command succesful, or a similar message, type exit at the command prompt, and then press ENTER.
Restart the computer.
Now try the website.
If this doesn't work then try these:
First thing. if you are using a router - that definitely looks suspect to me. Try and switch it off for about 10 seconds, to give it time to dissipate, then try the site again.
Next, for IE. (If this works we,ll try and sort out Firefox!!!) open Tools - Internet Options - Security.
For the sake of this test, lower the security level and untick (if it is ticked) "Enable Protected mode"
If that does not work, return the settings to the default, for the sake of continued security.
Go to Advanced and scroll down to "TLS 1.0" and untick it. If this works, then it is because the websites you are trying to access have not updated.
Other than that, I,m as baffled as you at this stage
P.S. Later.
It occurred to me, scraping back through the rustier parts of my brain, that there was, as far back as windows XP, one other problem. I thought by now it would have been automatically resolved. Sometimes it happens that a site (IP address) is not registered, or registered incorrectly, with another ISP. I know nothing about Verizon, but, if none of the above do not work, I would suggest you knock a little harder on their door.