Issue with Timelion error

I have used Timelion to generate Time series data. However, I have come across with errors when using split function.

This is my query without split .es(index='cpu-*',metric='avg:CPU(%)').mvavg(1,left) It runs fine and did generate chart.
However, when it comes to splitting .es(index='cpu-*', split=Hostname:5,metric='avg:CPU(%)').mvavg(1,left). It gives me the error of Timelion: Error: in cell #1: Request Timeout after 30000ms.

What could be the causes for that? I could not find what is wrong with my query

If you look in the network tab of your browser devtools, is the request to Elasticsearch taking a very long time? What happens if you issue the same request directly to elasticsearch from an http client like curl or postman?

Sorry, how should I use that with postman? I mean I don't know how should I query directly in ES for the average function and split funtion
What should I write after Get localhost:9200/map-*

I would look at your devtools network tab and see the details of the request it's generating