I got two of these P4 things. I found if I first use the DJI Assist 2 software on a computer that it seems to do other things to initialize before it operates correctly off the tablet. I think it asks to name your drone, set up an account, some agreements, etc. and then do the firmware update from it and not the tablet. The USB from the computer running the DJI Assist 2 into the P4, and the controller and the tablet sitting and turn on but no wired connection to the drone or the computer. After all that, then try DJI Go on the tablet.
Fwiw, the second P4 will be going back today to Best Buy if they have another. The first was one with a knackered up lens filter thread where it refused to come off (It just turned maybe 1/4" and then nothing beyond that.). It should unscrew freely so you can put other screw-on filters onto it. Might want to check it and there are a lot of videos out there on stuck Px lens filters, but if its bad from factory, good luck!
Second one has a misaligned lens where one side of whatever it's looking at sharper than the other side. You might want to check that before taking it into the air against some perpendicular fence or something to see how sharp the sides and corners are against one another. I sent the photos to DJI and they are going to issue an RMA as they think it is bad too. I might beat them to the punch and just take it back to BB and see if I can get a third P4 exchange rather than pay to send it off and wait for however long to get it back.
..and so far none have flown here yet! Sheesh! DJI QC seems to be an issue. Thirds a charm...maybe.
Good luck!
Mack-