Modpack importing will work fine if you use the Curseforge launcher exporting feature.
As long as the modpack exported file has a manifest and modlist file inside it will be fine.
That or if there is a conflict with a mod that isn't loading or has other issues which can happen which is why I couldn't have a modpack approved sometimes and just had to remove it/sort it out.
If they have the Curseforge or MultiMC launchers to import it they will be fine to import the zip file. I don't recommend just copying the mods folder of the Curseforge instance.
Otherwise if you can show some screenshots or anything else that could show the problem that would be great.