Before I go out to fly, since I use a WiFi only tablet and I cannot Hotspot to my smartphone, I always do several things. I perform a Setup, Device Maintenance, that cleans up all the trash and Apps that are needlessly running in the background, then I Restart the Tablet and I load the DJI Fly App and bring up the Satellite Map of the location that I will be flying to load the maps into the queue incase I need to find a "lost/crashed" drone and I want to actually see the trees, hills, houses, etc…
However, in your case I would also recommend doing a Cold Boot of all items (actually turn everything off, not just a restart…), Drone, the controller, and the device (phone or tablet). And make sure any friends, buddies, or family members (kids playing with a Nitendo) are not "packing…"
By the way, my hearing aids are WiFi and the drone has sometimes found them…
Also, make sure your device has both the WiFi and Bluetooth enabled, the DJI App active and then turn on the drone and then try to connect after the drone performs the self-test start up.
Is this a new problem or has it always been this way? Did you get a replacement Drone from DJI and now you have this problem? It makes a difference…