bmpashley

Thanks. The tool tells me that my site does indeed support http2. Following your suggestion, I disabled minify, and that works. I also tried re-enabling minify but with the Javascript files option switched off. That also works. So the issue appears to be with minifying Javascript files, but not HTML or CSS files. It was working fine until I upgraded the WP theme to the latest version.

Thanks for your help @properlypurple

Following your instructions with the Health Check plugin, I isolated the problem down to incompatibility with a particular plugin (WP-Optimize). I tried refreshing the WP Optimize caches and the browser cache but the problem continued, so I have disabled that plugin and posted the issue on the WP-Optimize forum for assistance. The theme is now working for me without that plugin enabled.