"site is experiencing technical difficulties" when customizing Euphony Pro

Hi, I just moved up from Euphony to Pro, and used Catch Web Tools to update and install the theme. But when I activate and either try to customize Euphony Pro or view Live Updates, I get an error message: "The site is experiencing technical difficulties. Please check your site admin email inbox for instructions." I've tried reinstalling Word Press 5.2.2, and deactivating plugins that I thought might be interfering, but no luck. I've checked the download on a test site running on Desktop Server, and it seems to work fine. My site is http://www.askpang.com/, running on a hosted service. Thanks, Alex Pang