Can't execute on server

When I’m trying to use the “Executes On Server” event after interacting with an object on the client-side.

Interaction blueprint
Debugging shows that it’s being skipped (“Using for Server” on the picture above.)
Server event
How can I fix it?

PS: I’ve already tried to use the “Switch Has Authority” node with a second custom event with “Executes On All” replication.

What is this blueprint class?
Not all classes can call server functions. E.g. Player Controllers and possessed Characters can, but regular actors cannot.

Yep, that’s an actor. What should I do to change this variable on the server from the client?

If you interact with it from the Character BP or the Controller BP, you can call the server function directly.