Not at all. There are no extra steps.
Here's how it works
1. Install via the Microsoft Store
2. Launch via Tile or Command as installed by the Microsoft Store
How did you install FileBot? How are you launching FileBot? Screenshots might help us understand what is different in your setup or usage that makes things go awry.
** All of the above applies to users who have purchased FileBot on the Microsoft Store, which is distinct and separate from standalone universal licenses. Make sure not to confuse the two licensing mechanisms. There’re completely separate and independent and each have distinct application binaries.
Error Code 15700
suggests that you're trying to run a Microsoft Store binary, but without launching it via the one of the standard Microsoft Store interfaces (i.e. Tile or Command)
which doesn't work. It'll work if you launch it via the appropriate Microsoft Store interfaces as explained in my previous reply.