Enhanced email option stopped working

I posted about this same exact issue not that long ago and I received a number of responses. I want to try again and maybe I can add a little more helpful information this time. I have been running the Cox Enhanced webmail option since I first started using Cox for my email with never any problems. On July 29 I was upgraded from Windows 8.1 to Windows 10. Right away I saw that IE11 (which had been my default browser) was running v-e-r-y s-l-o-w and took forever to load my home page IF it loaded it at all. After doing some research (try doing THAT with a slow browser that kept crashing) I read that others who had upgraded to Win 10 were experiencing the same problem and many were switching to either Google Chrome or Mozilla Firefox. I opted for Firefox. One morning about 10 -12 days ago I checked my email and closed out. About 1 1/2 hours later I logged back into my email and started getting a message: "Opps! can't find that page." or something very similar. I tried every avenue I knew to try and had no luck at all. I could access my webmail on my iPad but that's all I could do. I could not send any messages or check mail because if I tried I would get a message stating my logon id or password were incorrect. I verified that both were in fact the same as I had been using all along but I still got the same message if I tried checking or sending email. I phoned Cox tech support and after several hours and 3 people later I was still no further ahead than I when I first started. While on the phone with tech support person #3 out of frustration I checked the Classic webmail option and logged right in to my email. Classic would work fine but Enhanced not at all. Later that evening I started doing some more research and ensured I had all the correct up to date plug in's and that my Adobe Flash was current and up to date. On a whim I decided to try Google Chrome. I logged in to my email account on Chrome and my Enhanced webmail opened right up. I have Edge set up but not in use and I checked it and had Enhanced webmail there as well. I tried Firefox one more time but it was still not working there so I made Chrome my default web browser and thought I had the problem whipped. I logged completely out of everything, rebooted my computer and logged back in to my email and Enhanced was still working fine. The next morning I logged into my email and BANG! right back to the "Oops!" message and Enhanced webmail was back to non-operational all over again. I have tried everything I know to try but being as how my computer savy is a far cry from anything even closely resembling "expert" but more borderline "beginner-intermediate". Some things I know but a lot I don't. The simple stuff I can usually do pretty much OK but when someone starts talking "tech" I can sometimes keep up but more often than not I get lost. I have been told that Windows 10 and Mozilla Firefox don't play well together. I could not say one way or another. Microsoft Edge which comes bundled with Windows 10 and is supposed to be replacing IE down the road can't seem to play well with Windows 10 either since it was doing the same "now it works; now it doesn't" with Enhanced webmail as both Firefox and Chrome were doing. I have even went so far as to do a system restore hoping maybe if something may have gotten corrupted a restore would fix it. Nope. I did a refresh of Firefox. Nope. I re-downloaded and re-installed Adobe Flash Player. Nope. Why the Enhanced webmail started working the evening I tried using Chrome then by the next morning had reverted back to not working again is beyond me. I had responses from several individuals who stated they are running Firefox and their Enhanced webmail was working fine BUT one was using Windows 7 Pro and the other one never said. If anyone can possibly help me I would certainly appreciate the help. All I ask is PLEASE if you need to talk "tech" to me at least provide some layman terms I can follow. HELP!!!!