The activation doesn't appear for participate A in the Second section after the divider. If I remove the opt group, it works. Below is the code-
@startuml
hide footbox
participant A
participant B
participant C
== First ==
activate A
A -> B: Request
activate B
B ->> A : Response
deactivate A
opt condition
B -> C : Request
activate C
C-> B : Response
deactivate C
end -----------> remove this and it will work
deactivate B
== Second ==
activate A
A -> B: Request
activate B
B ->> A : Response
deactivate A
B -> C : Request
activate C
C-> B : Response
deactivate C
deactivate B
@enduml