I bought a Phantom 3 Standard that was a store return, which I thought just had a bad battery.  Got a battery and now it won't start up.  Just flashes red yello green, gimbal doesn't move and no video from camera.  No signs of damage or crash. Connects with DJI Go, and controller has  green connection light but light underneath the phantom for controller connect is flashing red.  Also get an IMU initialization error and barometer error at times.  Did IMU calibration and it said it was ok.  Any ideas, if not I guess I just gambled and lost.

What is the current firmware version, is it up to date? Besides, did anything happen before?

Try to start the whole system without the SD card in cam. If the app say no SD card then let pass the self diagnostic . Look for the movement of the cam. If the copter can pass this step then you may look in to the folders on the SD card. If you have a FW file on the card older than the FW on the copter then the self diagnostic step eats many time more than a minute.
Delete obsolete files or reformat the card via copter,and try to start up the system with the card in cam.