Hi There,
the theme 3.9.9 cannot be installed. I always get the message: "Update failed: There was a critical error on your website. Please check the inbox of your website administrator email address for further instructions and learn more about troubleshooting WordPress."
But there is no email in my inbox. All WPLMS Plugins are updated to the latest version.
Well in such case you can attempt to anually updating theme .
https://www.youtube.com/watch?v=fAxv6SwAgtw
please do not delete the old wplms folder just rename it .