HELP DESK [Milestones]

Dears we wanted to inquire about the milestones configuration for the HELP DESK, for your information, in the past it used to work well on the system, but now some stuff & some configurations weren't migrated accurately & fully from the OLD instance to the NEW instance & therefore the milestones now aren't working as they used to work on the OLD instance, so we wanted to ask how we can properly configure the milestones to make it work.

{NOTE: the OLD instance is no longer available unfortunately}

for the reference, these are some OLD screenshots on the OLD instance when they used to work: