We need some more details to understand what you might be experiencing.
Does this occur in a new project, or only your current project? Did you test this in Multiplayer Shootout sample project?
Can you be more specific about what you mean when you say Client1 can see Client2 “in distance” before Client2 can see Client1? Are you saying there’s a disparity between Client1 and Client2 when loading into a level, or when approaching each other in an already loaded map? What distance are we talking about?
What steps can we take here to reproduce this in a new project for testing?
Does this occur when Playing in Editor, or have you packaged game?
This is probably a relevancy issue. Try marking your characters as Always Relevant in their BPs under Replication, and let me know if that resolves issue for you.