There is an issue between the TDM/RTAS file in the TDM Effects V4 bundle (and the individual V4 TDM plug-ins) and the AAX Native versions that are included in that same installer that you would use in Pro Tools 11. This manifests itself when you save a session in PT11 and open it in PT10, assuming you are using the TDM Effects V4 license/installer. This would not be the case if you had a Soundtoys Native Effects V4 License, as that has a slightly different RTAS file. This was only uncovered with version 4.4.2, when we removed the 32-bit AAX files (for other bug-related reasons).
Here is one solution: You can bump back to version 4.4.1, which includes 32-bit AAX versions of all of our native plug-ins, and will allow you to open that session. Obviously, not being current is not optimal, but at least for this session that will work for you. Before you run this installer, you should uninstall your plug-ins using the utility in Application / Soundtoys / Utilities / RemoveSoundToys.dmg:
You could always reinstall version 4.4.3 after you're done with that session, as long as you don't have any PT11 sessions to open.