Reply to Flash

I just purchased my first full frame camera. The d750 bundle with the Nikon 24-120mm f/4 VR. I’m having issues with one or both. When the VR is turned on (on the lens) the built in flash will not pop up in auto when needed. If I’m in M or A mode, the flash will only pop up randomly if at all. And if it does, I can only take one shot and then the camera refuses to focus or anything really. But my 50mm seems to work fine in the same situations. And so does my 70-300mm VR lens.

I have 14 days to return or exchange the bundle to Best Buy but would really like to know if it’s the camera and/or lens or something I’ve done. Any help would be appreciated.

I do have a Godox speedlight that I will be using. But would like the built in flash to work since the bundle is only days old.