I note that the sample you show has a timestamp of 11:50 but that time is not within the graph range. Are you sure there is data in the db for the timerange you are showing?
If you believe there is then select the query and click Query Inspector. That will show you whether your query is returning any data.
I don’t know how it displayed like that. And it doesn’t display the data for Apr18.
And for Apr19, there is no data in the influxdb however it got displayed in the Grafana.
I am totally confused.