In some scenarios, business rules are not triggered when an update to last_discovered field is made on the CI record.
If the condition on the business rule is based on last_discovered (Most recent discovery) field, then the BR will not run for example, if the update is made by discovery (MID server user).
This is because, the update is not captured by the identification engine(IRE, Identification API). Since it is not, the update will not trigger the business rule even though the conditions match.
For example, if business rules are configured for 'last_discovered' field on the CI class and 'glide.identification_engine.batch_update_last_discovered' is not set to 'false' --> batch update --> No BRs triggered
Add "glide.identification_engine.batch_update_last_discovered" sys_property and set to 'false' if all the updates need to go through GlideRecord.