A copy that does not happen is not always a failure — most of the reasons are the copier doing exactly what it was told. Every one of them now leaves a line in the event log, so the question is answered by reading rather than by guessing.
The leader never fanned out
Not the leader
You traded on an account that leads no group. Check which account the group is led by — this is the most common one, and it looks exactly like the copier being broken.
Leader switched off
The account is the group's leader but its own switch is off.
Group paused
The group's status is not active.
Taken by hand
You clicked the trade in your broker's platform instead of it arriving as an alert, and hand-taken trades are not being copied on this server.
The fan-out ran and each follower was skipped
Rounds to 0 contracts
The follower's dollar risk divided by the stop distance came out below one contract. Raise the risk, or switch on "at least one contract".
Already at target
The follower already holds what the trade would have given it. Nothing to do, and that is correct.
Held by a risk rule
The line names the rule that held it.
Account locked
Follower disabled
That one follower's switch is off. A switched-off follower and a follower you never added produce the same silence.
Most of this is visible before you trade rather than after. The readiness panel at the top of the copier page names the blockers by name — see Copy readiness.
"No errors" does not mean "nothing happened"
A skip is not an error, so it is recorded at info level and the Errors filter hides it. If a trade seems to have vanished, read the log under All rather than under Errors.