Guys, maybe this will help. Drone was bought in 2016, had 1 flight, than month ago upgraded. So now i have same problem:
[00242782]Version checking[2]...
[00242874][03 06][00] v2.4.20.50 -> v2.4.20.50
[00242959][03 05][00] v34.2.0.9 -> v34.2.0.9
[00243010][04 00][00] v1.48.0.0 -> v1.48.0.0
[00243135][11 00][00] v1.8.0.0 -> v1.8.0.0
[00243262][11 01][00] v1.8.0.0 -> v2.0.0.33, firmware v1.8.0.0 not support.
[00243310][11 01][00] v1.8.0.0 -> v2.0.0.33
[00243413][12 00][00] v1.12.0.0 -> v1.12.0.0
[00243523][12 01][00] v1.12.0.0 -> v1.12.0.0
[00243628][12 02][00] v1.12.0.0 -> v1.12.0.0
[00243727][12 03][00] v1.12.0.0 -> v1.12.0.0
[00256275][15 00][00] device not detected.
[00256363][17 00][00] v1.1.1.7 -> v1.1.1.7
[00256483][17 01][00] v1.0.2.7 -> v1.0.2.7
[00256559][19 00][00] v1.0.8.96 -> v1.0.8.96
[00256604][01 00][00] v1.32.5432 -> v1.32.5432
[00256655][01 01][00] v1.32.5432 -> v1.32.5432
[00269202][08 00][00] device not detected.
[00269300][09 00][05] v4.1.0.0 -> v4.1.0.0
[00269347]Packet upgrade failed at version checking.
BUT! When i fly with the first battery, Everything is perfect, just there is no transmit, sometimes writes "weak signal" And when it out of energy i change battery, and the second one just magically turn transmittion on. I don't understand how it works. Just today tried the third time 1,7km away, and it was working perfectly. But when paste another battery it doesn't work. When i turn home both batteries don't work. Lookes like when smth hit up and it starts to work.
Check with multimeter whether the wires you soldered really provide 3.3V to the BT00/BT01 pins.
If they do, and the chip doesn't enter the boot mode - that would probably mean that the pins are not connected to the chip.