Have been trying to find some solution of late for installing the WebEx Chrome extension, but always used to get “Try Again” (in red) and it used to put me off. The only other solutions i adopted was to go back to IE or Firefox and try to open the WebEx recorded videos. But now found the solution directly from Cisco WebEx which resolved my problem.
The below guide should help you resolve this issue. Let me know if you are still facing any issues.