Monitoring page broken on master, No mapping found for [timestamp] in order to sort on

[LeeDr]

Kibana version: 8.0.0 master latest snapshot

Elasticsearch version: 8.0.0 master latest snapshot, TRIAL license

Server OS version: docker

Browser version: Chrome

Browser OS version: Windows 10

Original install method (e.g. download page, yum, from source, etc.): docker images

Describe the bug: Monitoring page doesn't render but instead shows error messages;

POST http://localhost:5601/api/monitoring/v1/clusters 400 (Bad Request)
...
kbn-ui-shared-deps.js:414 Possibly unhandled rejection: {"data":{"statusCode":400,"error":"Bad Request","message":"[query_shard_exception] No mapping found for [timestamp] in order to sort on, with { index_uuid=\"i2Yhb_zsRC6Tqt_tjIL5JA\" & index=\"metricbeat-8.0.0-2020.09.09-000001\" }: Check the Elasticsearch Monitoring cluster network connection or the load level of the nodes."},"status":400,"config":{"method":"POST","transformRequest":[null],"transformResponse":[null],"jsonpCallbackParam":"callback","url":"../api/monitoring/v1/clusters","data":{"timeRange":{"min":"2020-09-09T13:49:13.451Z","max":"2020-09-09T14:49:13.451Z"},"codePaths":["elasticsearch"]},"headers":{"Accept":"application/json, text/plain, */*","Content-Type":"application/json;charset=utf-8","kbn-version":"8.0.0-SNAPSHOT"}},"statusText":"Bad Request","xhrStatus":"complete"}

Steps to reproduce:

1. Install Elasticsearch, Kibana, (I also installed metricbeat, packetbeat, filebeat)
2. go to Stack Monitoring page
3. the page doesn't render completely. Error messages appear.

Expected behavior:

Screenshots (if relevant):

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

Any additional context:

I'm trying another non-docker setup. I expect it will have the same results. I'll update and post a screenshot.

[elasticmachine]

Pinging @elastic/stack-monitoring (Team:Monitoring)