Not really an MPQ Editor issue directly, but more likely your map. It's either protected or not compatible with the specific versions of Warcraft 3.
For the first case, there are several ways to deprotect the map, but it requires a time consuming and sometimes, you'll most likely caught by errors during the process.
For the second case, it's pretty obvious because when you save a map using Reforged World Editor, it will add an exclusive features that were only present in Reforged, meaning you can no longer open it with the older ones.
This thread might be helpful for solving this issue.