When you add something to the timeline a very thin green line appears. I believe this is a status bar / ribbon that indicates the clip has been buffered into VideoPadCache.
In the sequence preview window there is a status bar / ribbon that turns from blue to grey. I don't know what this means.
If I try to export before the bar is grey I will not get sound. I can sometimes wait for days for the blue to go grey before I can get a successful export. V11.08 Exporting 18Hrs. 4K/60fps
I believe it would be helpful, if a user tried to export a video before it was possible to do so, a prompt would appear telling them why. e.g. wait till the blue bar goes grey that tells when transcoding? is done AND/OR wait for the thin green line buffering? to be complete on all clips. AND/OR make it impossible to even try to do an export until Videopad is ready.