You can download and install the authext.dll if you are facing errors such as:
The program can't start because authext.dll is missing from your computer. Try reinstalling the program to fix this problem.
There was a problem starting authext.dll. The specified module could not be found
Error loading authext.dll. The specified module could not be found.
authext.dll is either not designed to run on Windows or it contains an error.
authext.dll is not designed to run on this version of Windows.
How to Install
Download and copy over authext.dll to the C:/Windows/, C:/Windows/System32,C:/Windows/System/, and C:/Windows/SysWOW64 directories.
Also copy it to the directory where your program is installed. If the program still shows the error, you might have to search on Google on where to copy over the authext.dll file.