Every single run an Agent makes — what it was told, what it decided, how long it took, and whether it errored or timed out — is recorded in the Audit Trail, found in Settings.
If an Agent seems stuck or silent, check three things before assuming something's broken: the master automation switch is on, the thread in question isn't already marked resolved or currently running, and the thread's most recent message isn't just the Agent's own prior reply sitting unanswered — all three are deliberate safety rails, not bugs. See Recover from a stuck agent for the full walkthrough.
Silence is also a perfectly valid outcome. An Agent that checks in, finds nothing worth acting on, and does nothing is working exactly as intended — the Audit Trail will show that run happened even though nothing visibly changed.