Should anyone encounter the same issue as above, here’s how the error was resolved for me:
A few days ago, I found a post in the UiPath forum, where it says to make sure that Studio and UiPath Assistant are the same version.
I updated both to make sure they were the same version (21.4.0 - which also matched the latest version of Orchestrator).
What I hadn’t done, however (and someone was smart enough to ask me), was check to make sure that the Activities package was also updated. Once I updated this through “Manage Packages”, everything ran smooth.