you can’t create multiclips this way, from a sequence, but I had a similar problem working with cameras that were not jam-synced during a 3 camera shoot. You need to get all you camera clips in sync with each other, using multiple video layers (however many cameras you have). first lay out your first camera. Then, use that as a guide for matching your second, third, etc… Once you have the first entire angle laid out, then load the first clip of your next angle into your viewer. find the exact frame that correlates to a frame in the first angle sequence. Once you find them, use the gang sync, top of viewer and canvas, to lock the two and scrub through to check picture sync through out the clip. If it is totally in sync, then overwrite onto V2, the next video layer up. Once you have these clips laid out, proceed to the next angle. You will end up with a sequence, with however many video angles you are working with. Make sure to cut in audio as well, if you have it on these clips, as it helps with fine tuning sync. After you are sure the entire program is synced between the multiple angles, then export each video layer with it’s respective audio as a it’s own quicktime reference movie, using same as current settings. Re import these new full clips into your project, choose all, select modify and make multiclip based on in points. If you have a long program, break the new master clips into segments, giving it handles to ensure you have enough space to adjust if need be. Good luck!
p.s. this is not the correct way to do this, but a viable work around in a pinch. Main point is to make sure you get jam-synced masters as the original files, or create your synced multiclips before you start editing.