90% of all the MP4 or MOV files I’ve tried to import into 13 are reported as “invalid or not supported file!” in the Import Video dialog, including the file I’ve been using since March in Cubase 12 (which, btw, was a special low-bitrate version so Cubase 12 would even play it smoothly). Most, if not all, are H.264, various sizes, bitrates, etc. Maybe Steinberg has given up on supporting video post?
Major fail, Steinberg. At least your Store works. (sadly) 
Could you attach a small problem file here for SB devs or others to examine please.? If there are privacy concerns, maybe PM (private message) one of the forum mods directly, pointing to this thread. You will need to zip up the file first before attaching.
Haven’t seen any changed system requirements for handling video from C12, other than improved H.264 hardware decoding.
(Not upgraded yet, so can’t offer clues/help personally).
Hi,
Or attach just the (short) video file, please.
But that is exactly what I’ve just suggested above Martin…?
Hi,
Sorry, I was reading “project”… Probably too much reading and writing on the forum with the Cubase 13 release, now.