Hello. I have a project where you can take an object in your hands using an attach component to component, and there is also the ability to open a door. I added multiplayer to this project, but when I take an object, it appears in my hands, but on behalf of another player, the object does not disappear and does not appear in my hands. There is a similar situation with doors: I interact with the door, but it does not open for me, but it does open for another player. Here is the question: how to make all these mechanics work on the server? Thanks.
Multiplayer is harder (when hit), than it looks from afar 
I would suggest you get really, really familiar with Networking and Multiplayer in Unreal Engine | Unreal Engine 5.5 Documentation | Epic Developer Community
Other than that - I am assuming only one of your clients attaches the object. What must happen:
- The request for attaching must reach the server through a RPC.
- The server must notify all clients to do the same attachment either through replication or through a multicast event.
Hope it helps and happy reading