When patching your game with the launcher, you may encounter an error Old File Not Found. This particular error can be confusing to some people as it means there's not an issue with the patch you're installing, but the game installation that you already have.
When the Mortal Online launcher updates your game with a patch, each patch contains only the data to change the file from its last version to the new one. It changes each file from A to B so that it doesn't have to store the entire file and thus patch files are as small as possible. The problem with this is that the old file needs to be exactly what it expects in order for it to know how to change it into the new one, and this is where your Old File Not Found error comes in.
There are two common causes of this error:
Not enough disk space
Because each patch backs up data before it applies, in case something goes wrong, it requires more space than you would expect on both your Windows system drive and the drive Mortal Online resides upon, if they're not the same. Try freeing up more space and trying again.
Security software interference
Internet security and antivirus programs, if set to be too strong, can sometimes cause interference with a patch installation. Try disabling these systems just temporarily to install the patch, or even boot into Windows Safe Mode with Networking to make sure other software isn't interfering.
This error can also sometimes indicate a corrupt file in your game installation. To find out exactly which file is damaged, check the knowledge base article Tracking Down Errors. If you have a friend who has this file and can send it to you, it may bypass the error. Otherwise, a reinstallation of your game may sometimes be required (see Reinstalling Mortal Online).