Hello chasealexander and welcome to the forum.
I am sorry to hear about the problems you are running into.
But without any details of the problem and what steps you have taken so far we would only be guessing and could take you off down the wrong path.
Anyway:
-- forget MPC for the moment, stick to the ST3 standalone program
-- do any instruments load into that program?
-- what happens when you try to select and load an instrument?
-- in ST3 Settings / Sound Content, what is the full path to the ST3 Sound Library
-- what is the full path to the installed ST3 Sounds Library?
-- what is the full path to the installed Steel Drums Library?
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As this is primarily a user to user forum, someone-else may chime in [#]. Meanwhile, the best thing to do is raise a
Support Ticket, here for some one to one investigation and help (US (East Coast) Business hours, generally). Response time is usually within 2 working days, but in the current circumstances please allow some more time.
[#] But please remember that the same symptoms do not necessarily mean the same problem.