Hey Jack,
I'd first off check if there's the data you expect in Elasticsearch by seeing what indices exist using the API: _cat/indices?v.
If you're not seeing any indices being created you could enable debug logging on your Elasticsearch logstash output (https://www.elastic.co/guide/en/logstash/current/logging.html), or even run a tcpdump from your logstash server to monitor outbound traffic to Elasticsearch.
You could do similar on your inputs to ensure Logstash is actually receiving any metrics. I'm not familiar enough with filebeat to know what it should log by default, but perhaps there's some logging you can adjust there to ensure it is reading from files correctly?