That’s an interesting problem.
What Aseprite version are you using?
Do the files have sequential names?
Are you able to open the first file in the list with Aseprite like you would any other file and have it try to prompt then to open as an animation? That piece is built into Aseprite, so I’d be interested to see if that works.
I’m going to test on my PC when I get some free time but hoping we can figure out what has gone wrong.