Are you talking about MQL5 VPS for MT4/MT5?Changing the VPS server?
As far as I know (from MQL5 VPS Rules) -
Products purchased at the Market do not require additional activation for working in the Virtual terminal. The number of a purchased Product's available activations is not decreased.
As to changing VPS server inside MQL5 VPS service - no idea, but it may be same: activations are not decreased.