FMSProxy is a small program that runs in the background and is connected to the High-Logic Font Management Service (fontservice). It acts as a doorway between the fontservice (running as administrator) and your user environment where your fonts are installed. The 3 main tasks of FMSProxy are:
Notify the fontservice of changes in the loaded fonts
Load and install fonts for plugins
Retrieve fonts from the network that the fontservice can't access
What happens if FMSProxy is not running?
MainType won't be able to access fonts located on the network and plugins won't be able to load and install fonts.
Why do I keep getting notifications in MainType that FMSProxy is not running?
When you install MainType, FMSProxy is also automatically installed and set to run each time you start your computer. Some programs and system optimizer software may remove FMSProxy. Try to reinstall MainType over your existing installation as that usually solves the problem.
How can I see if FMSProxy is running?
The easiest way to see the status of FMSProxy is to start the font management service configuration utility (FMSConfig). You can find it in Windows start menu, but for your convenience you can also access it through MainType's main menu (Tools -> Create and Restore Backups). The status of FMSProxy will be indicated by a small icon.