Quick answer: Unreal OnRep function not called for the initial replication when actor first appears? OnRep fires on changes; initial isn't a change - check default value.
Replicated bool defaults to false; OnRep fires only when server sets to true.
Set value in OnInitialReplicated
Custom event fires once; manually trigger OnRep logic.
Or default to opposite of expected
Default = false; server immediately sets true. OnRep fires.
Audit OnRep semantics
Each OnRep: initial behavior documented.
“OnRep is change-based. First-time isn't always a change.”
If you depend on OnRep for initial setup, the default-flipping pattern is the safe workaround.