1 is easy to imagine - a large enough collapse that making new ones is very very hard, especially compared to scrounging and repurposing the huge amount of existing ones. Imagine a huge population decline, and search parties looking through the ruins for useful tech, like computers, decades later.

Such a society could probably make new computers, but the cost of making new, much worse specced computers, may not be cost effective for a long time as long as old computers can be found and repaired.

Edit: such a movie or novel would make for great Fallout-ish world-building. Imagine for instance a large hotel in a big city running the booking system on an old laptop in a central secure location, and new 8-bit computers used as terminals at the front desk. Public access 8-bit computer terminals at public libraries connected to copies of WikiPedia running on some old gaming rig and such things. :-)