Problem of connecting mission planner via bluetooth (APM 2.6

Hi, since my 3DR radio was broken, i’m know trying to connect MP via blue tooth device(HC-06).
however, after 3 sec from pressing “connect” button, it always show that “connect fail” (LED on HC06 still blinking )
and today I saw someone solved this problem with updating the MP to the latest version(1.3.7), so I did it as well.
Then, it’s weird that the window know showing “trying to connect, time out in _ sec” (detail info see attachment below)and the LED on my HC06 go solid, seems like they’ve found each other, but just can’t connect.
Could any help me figure out what’s wrong here? Thanks.
(I’v changed the baud rate of device to 57200, and set the baud rate of MP to 115200)
btw, the voltage of Pin TX RX at the telemetry port is 4.0V, is that normal?

please try the latest beta.