What need to be done to make the group for VLAN 101 function properly?

Answer: See the explanation.

Explanation:
Enable preempt on the VLAN 101 HSRP group on DSW1
Issue the “show run” command and you can see that the “standby 1 preempt” configuration
command is missing on DSW1. This is needed for it to become the active HSRP router
immediately.