Hi @mitchlm 

FYI ->Keeping PDIs Available for Active Builders: Upcoming PDI Reclamation Changes

As per above article , 

reclaiming PDIs that meet both of these conditions: 

• 90 days or older (based on when they were provisioned) 
• Haven't had a PDI login in the last 10 days 

Please check this Personal Developer Instance (PDI) Guide

Where it is written-

"When a PDI is reclaimed, the instance is unassigned from you, reset to its original state, and reassigned to another Developer Site user. Reclaiming instances allows ServiceNow to supply active developer site user with free instances."

Once it is reclaimed, only option is left i.e Request for New PDI instance.