A copy that does not happen is not always a failure — most of the reasons are the copier doing exactly what it was told. Each of the reasons below leaves a line in the event log, so the question is answered by reading rather than by guessing. One case is easy to miss: a trade you place by hand on a leader whose hand trades Tradeus cannot copy — today that is Alpaca, which owns what it buys. Tradeus does not see that trade at all, so there is nothing in the log to find. The readiness panel is the only place that tells you, and it tells you before you trade rather than after. Its headline reads Not copying in that case, although the orders from your alerts are still copied.
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 copying hand trades is switched off on the server. Alerts still fan out.
The fan-out ran and each follower was skipped
Rounds to 0 contracts
The follower's risk amount divided by the stop distance came out below the smallest size that instrument trades in. Raise the risk, or switch on "never smaller than the instrument trades". On MetaTrader that switch works from the lot rules your own terminal reports, so it needs the current program in the terminal; where a broker publishes no size grid for an instrument at all, the switch has nothing to round to and is skipped rather than guessing at a whole contract.
Already at target
The follower already holds what the trade would have given it. Nothing to do, and that is correct.
Held by the kill switch
The kill switch is on, and it holds every new entry until you release it — a server restart does not lift it. Pressing it also paused every group, so you meet this line only after resuming a group with the switch still on. The line names it. See The kill switch.
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.
Different market
The follower trades another market than the leader — a futures account in a TradeLocker group, or the reverse. It is skipped on entries, exits and hand trades alike, the readiness panel shows it as blocked rather than armed, and the line says which market each side trades. Groups built before this check existed can still contain one; remove it from the group.
No such instrument
The follower's broker has nothing under that name. The line names the symbol — add a mapping, see Symbol names per account.
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.