What can trigger a rule

A trigger is a record type plus an event on it. Events are not shared between record types — each type supports its own list, and picking an event that does not exist for that type is the most common reason a rule never fires.

What each type supports:

• Opportunity — created, stage changed, a custom field changed, a date reached
• Customer — created, updated, a custom field changed, went quiet
• Lead and contact — created, updated, a custom field changed
• Activity and task — created, completed, a date reached; tasks also on status changed
• Invoice — created, overdue, a date reached
• Subscription — a date reached
• Ticket — created
• Project — created, completed, stage changed
• Document — signed, declined
• Form — submitted
• Sales sequence — enrolment created, completed, or replied to
• Checklist — an item completed, or the whole checklist completed
• Resource — over-allocated

Two worth knowing about specifically:

Custom field changed is how you automate on your own fields — a KYC status reaching compliant, a contract status changing. You name the field, and you can narrow it to one specific transition rather than any change, which is usually what you want.

Went quiet fires when a customer has had no contact for a while, which is the one trigger that fires because something did *not* happen.

If the event you want is not on this list for the type you want it on, the rule cannot be built that way. Borrowing an event from a different record type looks plausible in the builder and produces a rule that silently never runs.