Hi there,
Returning to OM after a hiatus from music making and of course I had to get back up and running with one of my favorite tools, OM!
I was very excited to see a new release of OM 7.1.0.0. However, after installing I was met with an error regarding loading certain .DLLs. In this case, it was the sdif.dll. I recall running into a similar issue when trying to install OM originally on a previous machine. I do not remember what I did to solve the issue.
This time, however, I was able to solve the problem! I utilized the utility posted here. Which pointed me to a missing DLL. Great! I was able to download and copy the missing file to my system32 folder. No luck though, as my OM still gave an error when opening. It was then that it dawned on me that the issue could possibly be related to missing dependencies from a past Visual C++ Redistributable. I went ahead and looked up “download all visual c++” and proceeded to install all VC++R’s from 2005 to 2022. This was easily done using a batch file. I rebooted my computer and the problem was solved! OM no longer gives an error, my MIDI playback works, and I am back in business. 
I know this may be old hat or obvious to those more familiar with OM or those that have more experience dealing with such issues. I believe that in documenting my problems and solutions it may pose useful for others in the future.