So, it's Android and you have downloaded the latest Fly version from DJI.
Your new phone, for whatever reason, may not be compatible with the newest Fly version. What Android version is your newest phone on?
I assume the Fly app on your older phone still works?
Do you still have it?
Any way to copy the version of the Fly app on your older phone to the new phone to see if that works? On iPhones, when upgrading, it copies the version on the prior device, rather than forcing you into downloading a newer version.
Also, what drone?
Have you also updated the FW on the drone to the latest FW?
The older FW on the drone may not compatible with the newest Fly version.