You need an Actor Object Reference to cast “From”.
Nothing → Cast to What Ever… Will always fail. Essentially the actor must exist in the world. Either placed or spawned.
Get all actors of class searches the game world for instances of said class. Where you call “Get all actors of class” matters.
If on the Autonomous player (controlled local client) you’re searching your simulation of the world. If on the server you’re searching the servers simulation of the world.
For example if your locally owned character spawns an actor and the server runs get all actors of class for it…it won’t be found. If the server spawns an actor and it’s not replicated, you won’t get a result locally.
Always “validate” your reference before casting.
My reference → Is Valid → Cast