Hi please help.

I finished my first drone and now i have the problem that it does't arm. The OSD ist shown everyting right and the googles also show the right voltage. In Betaflight the arm button is working.

 I have 6 UARTs and chose UART2 as serial rceiver, how the manual told me. The MSP connection is enable for QARTS 1 &2 with 115200. I also put peripherie for UARTs 1&2 on VTX ( MSP+Displayport). That was the only combination my googles show the OSD right and my DJI Remote 2 is still working. 

i have the speedybee 405 v3 with the Airunit 3 ans 6S. The Airunit stays in low power mode and has only 6 mps. 

Would be nice if someone can help me to fix this.

there should be a betaflight warning in the osd, at least on qn analog quad

try to arm it, without rotors, if it doesnt; connect it to betaflight, watch for arming disable flags in the first top on top right or go into cli tab and type "status" copy paste inhere