NUENDO 13 Video export

Dear Steinberg Nuendo family,

I find quite bizarre the fact that I can’t re-import any video that I previously exported with Nuendo!

Nuendo will import any MP4’s from the several editors I usualy work with, but, the moment I export a project with Nuendo and try to insert it back onto my timeline I get a “no sign”

Does anyone know the reason why it might be?

Thanks in advance!
JMB