When disabling the light version of Outlook Web App, you are also disabling the blind and low vision experience feature. If a user chooses the “Use the blind and low vision experience” option when entering OWA for the first time, OWA will give an error that the user must update the browser to the latest version. OWA is not usable for the user from this point. Disabling the light version of the Outlook Web App is not removing the “Use the blind and low vision experience” option. Is it a bug? I don’t know, yet.
Use the following commandline to enable the Light version of OWA again.
Set-OwaVirtualDirectory -Identity “Server1\owa (Default Web Site)” -OWALightEnable $true