Or it had failed.

MakeMKV is free while in beta, but the key is time-sensitive. If you haven't used the program for a while and get an error saying your key has expired, you'll need to get the current key from the official MakeMKV forum announcements.

When the download fails, it is rarely a problem with MakeMKV itself, but rather a disruption in the communication between your computer and the MakeMKV server. Common causes include: