Your Videos don't play!

Note: In general Chrome is by far the best browser to use. 

Chrome

In the browser bar, enter:
chrome://settings/clearBrowserData
Select the following:
Browsing history
Download history
Cookies and other site and plug-in data
Cached images and files
From the Obliterate the following items from: drop-down menu, you can choose the period of time for which you want to clear cached information. To clear your entire cache, select the beginning of time.

Click Clear browsing data. Close all browser windows and re-open the browser. 

Firefox

Firefox has opted for almost no tracking by default, really to thwart re-targeting ads, but they cast a net that picks up other unrelated stuff too.  Our video host needs to be able to identify that you have permission to view the video.  
To fix this:
1. Click the lock symbol shown below 

2. Disable the protection for this session

3. The videos should now work perfectly in Firefox :)

If this doesn't solve the problem try clearing your cache etc by following the below steps.
From the History menu, select Clear Recent History.
If the menu bar is hidden, press Alt to make it visible.

From the Time range to clear: drop-down menu, select the desired range; to clear your entire cache, select Everything.
Next to "Details", click the down arrow to choose which elements of the history to clear. Click Clear Now. Close all browser windows and re-open the browser.

Internet Explorer 8 and higher

From the Tools or Safety menu, select Delete browsing history....
If the menu bar is hidden, press Alt to make it visible.

Deselect Preserve Favorites website data, and select:
Temporary Internet files or Temporary Internet files and website files
Cookies or Cookies and website data
History
Click Delete. Close all browser windows and re-open the browser.

Opera

From the Opera menu, select Settings, and then Delete Private Data....
In the dialog box that opens, select the items you want to clear, and then click Delete. Close all browser windows and re-open the browser.

Safari  

Safari 8

From the Safari menu, select Clear History and Website Data....
Choose the period of time for which you want to clear information, and click Clear History.
From the Safari menu, select Preferences....
Click Advanced.
Check Show Develop menu in menu bar and close Preferences.
From the Develop menu, select Empty Caches.
Close all browser windows and re-open the browser.
Safari 7 and below
From the Safari menu, select Reset Safari....
Select the items you want to reset, and then click Reset. As of Safari 5.1, Remove all website data includes both cookies and cache. Close all browser windows and re-open the browser. "

Android

Note: The steps to clear your cache, cookies, and history may differ depending on the model of your Android device and your preferred browser.You should be able to clear your cache and data from your application management settings menu:

Go to Settings and choose Apps or Application Manager.
Swipe to the All tab. 
In the list of installed apps, find and tap your web browser. Tap Clear Data and then Clear Cache. Close all browser windows and re-open the browser. 

Apple iOS

Note: The following steps apply to the newest version of Mobile Safari for iOS. If you need instructions for older versions, you might find them in Apple Support's Safari web settings on your iPhone, iPad, or iPod touch. 

Open your Settings app. 
Tap Safari. 
Tap Clear History and Website Data and confirm. Close all browser windows and re-open the browser. 

Information from:  https://kb.iu.edu/d/ahic