I had a crash the last time I flew my drone and this issue happened after that. Whenever I try to take a picture or switch from picture mode to video mode, it appears that there is No Image Transmission Signal.......I tried to update the firmware but there is no luck...... Can somebody help me? I need it for my work......

test turn off your wi-fi connection (if on)

I had a similar problem. You can also test with another memory card. it may be that what you are using is with some damaged track so it takes so long to capture the photo or change the capture mode

Send back to repair.  

Check all cables to gimbal board make sure you hear  a click off both

Sorry to read the crash. It is recommended to start a case and send the unit in for diagnosis. Please kindly start a case from here and arrange at your earliest convenience: https://www.dji.com/support

Hi, did you find out what ther problem was? I have the same problem now

I've just had the same problem. Used a different memory card and now it's working.