I’m not getting a link that says click here to contact Jetpack support, but expanding the red banner that says “It looks like your site can not communicate properly with Jetpack” indicates the error is: XML-RPC is not responding correctly ( 404 ), which is #4 on the self-diagnose list. Clicking the provided link does give me a 404, so it looks like I need to contact my web host.
Thanks for leading me in that direction.