new mavic pro 2 days old. no video or pics to sd card or phone display. tryed wifi and rc. did work once for a short 3 sec. video and 4 pics. will they do an express exchange ?

try changing the SD card and format it in the AC

Just to verify, do you mean that the phone doesn't have the video feed, the pictures and videos also won't save on the SD card? If yes, please confirm what the app says, or provide me with the screenshot of the app. If it displays "Disconnected", please check if the connecting cable is loosened, change another cable or another mobile device, and for the videos and pictures on the SD card, please try to format it and check if it works again, please back up the importance files before formatting it.
If the issue persists, it would be nice if you can provide me with the operating video, I would like to check more. Thank you.