Footage won't load sometimes (red node - "no clip")

I have pretty average composition, and it seems that fusion is overloaded or something, it won't load a clip I drag on the graph, the node will be red marked and the mention "no clip" is displayed in it.
If I try another footage, it loads, I try a third footage it won't load (?!) It appears to prevent some footage to be loaded on a random basis.
If I open the same footages in a fresh fusion session (at the same time of this one), they load and play.
What to do?
Ram usage is still low and there is room, it is really ununderstable.
Thank you for helping.

Are you viewing it on the first global range frame?

Lol, you are teaching me something here, what is this? Sorry for the noob question.

What frame are you on when you are getting the error?

I don't remember where I was, and now the problem is gone (temporarily?), and when I hit play the nodes get played and turn green, but I know it's gonna happen another time, since it happened in the past, so I would like to understand. Is it because ressources are limited so fusion prevents caching or something?

No, its usually just being on the wrong frame.
If your network is very slow it might time out, but it would need to be pretty bad.

ok thank you for this. So if I understand, footages have to be synchro?

No, you just need to give Fusion a chance to figure out how long the footage is.

Thank you very much for your explanations, I understand better the situation now

This issue was driving me crazy. I'm using a very high end PC: AMD Threadripper Pro, 256 GB RAM, High Speed NVME, Dual 3090s! It turns out the solution for me was to change the format and codec for my VFX connect clip. I was using VFX connect to work between resolve studio and fusion studio. After changing the format to: MXF; the codec to DNxHR HQ: my issue has been resolved.