Error: The filename or extension is too long.
AltStore on Windows can't handle installing apps that have long file paths in them.
Same thing happens when trying to sideload directly with AltServer.
When installing the same app using signing services or a private certificate it installs without any issues.

@rileytestut take a look at this it might help:
.NET 4.6.2 and long paths on Windows 10
It says that the "app must have a specific manifest setting" so in addition to Enabling Long Paths support on Windows the app (Altstore) needs to be modified to add the manifest setting to work with the long path support setting.
I'm not sure of the language Altstore is written in or the specific developing stuff but this might give you an idea on how to fix the long filename error.
yo @rileytestut is there any update on this? i'm a beta tester and was shocked to see this still not working