Mac 10.9.5 Zwift Launch Issue

I downloaded Zwift for the free trial and it all went well. A week later I have upgraded to the full one month sub. but when I click the App icon on my mac the Zwift window appears but stays completely white - no options to login or anything.

I uninstalled (deleted app) and redownloaded, shutdown and rebooted, etc, but still the same issue.

Any help would be greatly appreciated.

A post was merged into an existing topic: White screen on app launch