Windows 8.1 and Internet Explorer have elevated the level of unworkable software that microsoft has released to heights that even THEY may never reach again, but I won't hold my breath on that one.
Your problems can be summed up with three words:
That doesn't mean a lot, I'm sure, but it's the root of your problems, and Flash Player has nothing to do with it.
Microsoft "rewrote" the User-Agent Strings for the abomination they call their latest and greatest browser. User-Agent Strings are what websites use to identify the browser you're using and provide the proper content for it's browser engine, like ActiveX stuff, and Flash or HTML5 video. Thanks to the geniuses in Redmond, WA, the User-Agent Strings for IE11 (which has a Trident engine), ID it as either "Gecko" (Firefox) or "Webkit" (Chrome). Problem is: when the site the directs to the content for one of these two engines, the Trident engine in IE can't intepret it and the site then sees IE as an "unidentified" browser.
The problem with an unidentified browser is that the plug-ins in that browser aren't recognized either, so even though you're up to date, it says you need the latest Flash Player when you use IE11. YouTube... has converted to HTML5 video so if it doesn't detect Flash Player, it can display HTML5 (MP4) video which requires no plug-in to play. Facebook can't do that, because HTML5 doesn't apply to games... only video.
Microsoft has no plans to "fix" the mess thay've created because they think it's a great idea to block you out of the websites you visit.
They recommend using "Compatibility View" and pretending that you're using an older verison of IE... Problem with that is that it's seen limited success, and you have to enable it for EVERY page that has problems... individually.
I'm not big on "pretending" so I recommend actually using another browser.
ANY of those will work where IE11 won't, with the Flash Player Plug-in (For all other browsers), and Chrome doesn't even need that because it has its own Flash Player plugin built in.
While this is fine for some of my problems, it doesn't work on the things I need it to. I use quickbooks for my business and it is running internet explorer when I am trying to open something inside of Quickbooks. Now I can't open the stuff I need because of the flash player problem and I can't figure out how to switch it to a different browser. Also, some of the government websites I need to report to also don't work with other browsers and I am not sure if I will have a problem with that.
QuickBooks will use WHATEVER browser you set as your default. Trust me. I worked for Intuit for four years, in TurboTax and QuickBooks.
ALL Intuit products that connect, use the "default" browser when they connect. They are not "beholden" to Microsoft, or Apple, or anyone.
I appreciate the your help but had to get the problem fixed another way. Quickbooks kept using IE no matter what browser was default. Here is how I finally got it fixed. After you told me it was a problem with IE, I tried to contact Intuit for help, but didn't get any response. So then I went to microsoft support for IE help. Got online chat support and we reset IE to original settings. That didn't help. I got back on Adobe website and downloaded the update for Windows 8.1 with 64 bit for my system. When I tried to run the update, it said that it was already installed (KB2938527). So I figured what the heck and I went into the control panel and uninstalled the update (KB2938527). I figured I could reinstall if necessary. After uninstalling that update, my problem went away.