If this error occurs when trying to carry out RTI submission it may be due to .NET not being fully installed, especially on NEW window 10 PCs whereby .net 2.0 and 3.0 are not automatically enabled.
See response from Pegasus:  

This message: "Unable to initialise HMRC mark component" occurs if .NET version 2.0 is not installed.

Switching on the Windows feature .NET 3.5.1 will include both .NET 2.0 and .NET 3.0. You will then usually need to reboot the PC in question, uninstall OFM and then install it once .NET is in place..

One of our partners had to turn the .NET feature on, uninstall OFM and reinstall before the message went away. This would be the case if the customer had switched on .NET 3.5 AFTER installing OFM not before.