in my case my dashboard file .json have wrong uid of datasource
“datasource”: {
“type”: “prometheus”,
“uid”: “P1Exampleuid”
},
then I changed the value of uid with right uid datasource the result my dashboard can show data automatically after imported, and this issue can be solved too with remove all uids at dashboard json file.
and for quick to know your datasource uid you can open your grafana dashboard and click datasource and at address bar of you browser will show the uid datasource.
sorry for my english