Posting this in case anyone else experiences this.
I think I had an older version of Spark, and tried to upgrade, but then the app wouldn't show anything. No pages, and very curiously, no errors in the console.
Eventually I tracked it down to something involving the
v-cloak directive. No link was turning up anything that was explaining what was happening. So I did a fresh install of Spark and everything was working. So I began trying to find what was causing the problem.
Looks like Spark was built before Vue 2.0, and was using inline-templates, and maybe there was another change that the
v-cloak directive needs to be on the actual Vue instance div.
In older versions of Spark, the
v-cloak directive was on the
body tag, and moving it to the the
spark-app div, then the site begins appearing again.
Unfortunately, this does not seem to be mentioned in the upgrade guide.