Please don't use Internet Explorer version 11.x, try to use Chrome or Firefox instead or earlier versions of IE, because of it's new default settings..
If you have to use it please do the following methods given below:
Method 1: Disable software with invalid signature to run in Internet Explorer
a) Open Internet Explorer browser from Desktop.
b) From the menu bar select Tools Select Internet Options.
c) In the Internet Options window, select Advanced tab.
d) Scroll down and un-check the Allow software to run or install even if the signature is invalid
e) Click OK to save the settings. Then close the Internet Options window.
If the issue persists, try resetting the Internet Explorer and check if the issue persists.
Method 2: Reset the Internet Explorer.
Click the link and follow the steps “How to reset Internet Explorer settings”
Microsoft KB Link