No messages in the browser console. I get the same failure for all of the sample data sets. These seem to be the relevant kibana logs:
{"type":"log","@timestamp":"2018-12-25T02:24:38Z","tags":["warning"],"pid":6566,"message":"Unable to create sample data index \"kibana_sample_data_ecommerce\", error: Request Timeout after 30000ms"}
{"type":"error","@timestamp":"2018-12-25T02:24:38Z","tags":["warning","process"],"pid":6566,"level":"error","error":{"message":"Error: Status code must be an integer\n at Object.exports.assert (/usr/share/kibana/node_modules/hoek/lib/index.js:740:11)\n at module.exports.internals.Response.internals.Response.code (/usr/share/kibana/node_modules/hapi/lib/response.js:105:10)\n at handler (/usr/share/kibana/src/server/sample_data/routes/install.js:131:32)\n at <anonymous>","name":"UnhandledPromiseRejectionWarning","stack":"UnhandledPromiseRejectionWarning: Error: Status code must be an integer\n at Object.exports.assert (/usr/share/kibana/node_modules/hoek/lib/index.js:740:11)\n at module.exports.internals.Response.internals.Response.code (/usr/share/kibana/node_modules/hapi/lib/response.js:105:10)\n at handler (/usr/share/kibana/src/server/sample_data/routes/install.js:131:32)\n at <anonymous>\n at emitWarning (internal/process/promises.js:65:17)\n at emitPendingUnhandledRejections (internal/process/promises.js:109:11)\n at runMicrotasksCallback (internal/process/next_tick.js:125:9)\n at _combinedTickCallback (internal/process/next_tick.js:132:7)\n at process._tickDomainCallback (internal/process/next_tick.js:219:9)"},"message":"Error: Status code must be an integer\n at Object.exports.assert (/usr/share/kibana/node_modules/hoek/lib/index.js:740:11)\n at module.exports.internals.Response.internals.Response.code (/usr/share/kibana/node_modules/hapi/lib/response.js:105:10)\n at handler (/usr/share/kibana/src/server/sample_data/routes/install.js:131:32)\n at <anonymous>"}
{"type":"error","@timestamp":"2018-12-25T02:24:38Z","tags":["warning","process"],"pid":6566,"level":"error","error":{"message":"Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 8)","name":"UnhandledPromiseRejectionWarning","stack":"Error: Status code must be an integer\n at Object.exports.assert (/usr/share/kibana/node_modules/hoek/lib/index.js:740:11)\n at module.exports.internals.Response.internals.Response.code (/usr/share/kibana/node_modules/hapi/lib/response.js:105:10)\n at handler (/usr/share/kibana/src/server/sample_data/routes/install.js:131:32)\n at <anonymous>"},"message":"Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 8)"}