The new priority value takes effect immediately but does not affect the current active switch. The new priority value helps determine which stack member is elected as the new active switch when the current active switch or the switch stack resets. Reference: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/software/release/16- 5/configuration_guide/stck_mgr_ha/b_165_stck_mgr_ha_9300_cg/managing_switch_stacks.html