I am a long time DJI drone user and when I changed my phone on login with my DJI account to the DJI GO 4 app, all the data were reset.My flight records are now 0 minutes, 0 meters, 0 flight, LV0.

How to solve this?

Hi, we're sorry for the inconvenience. I would recommend syncing the flight records using the DJI Go 4 app on your previous mobile device then use your new phone to see if there will be changes. Please note that if the application was deleted prior to syncing the flight records, I'm afraid that the flight records and videos would be deleted as well. Please let us know the latest progress. Thank you for your support.

Did you sync your flights from the older phone and resync to the new phone yet?
If not then do that.