Mike, I understand what you mean by a perpetual license. A legitimate perpetual license does not normally expire after a year or require you to keep paying a subscription.
The problem here is not the word “perpetual.” The problem is what type of license the seller actually gave you.
Microsoft Office Professional/Professional Plus licenses are organization/volume-license products rather than the normal retail products sold to individual home users. For an individual buying Office 2024 outright, Microsoft's consumer products are Office Home 2024 and Office Home & Business 2024. Microsoft will NEVER sell you a Professional Plus license. Volume license is not perpetual license.
A third-party seller can sell you a product key and call it a “perpetual license,” but that does not necessarily mean they sold you a legitimate retail license that belongs permanently to you.
For example, the key could have come from an organization's volume-license agreement. It may activate initially, but if that organization's license is later revoked, exceeds its permitted activations, or requires validation against that organization's licensing system, your copy can stop activating. The message telling you to contact an administrator is another clue that this is an organization-managed license.
I am quite certain that you bought it from a third party seller. You would need to contact that seller for a refund if they sold you a volume-license key as a personal perpetual license.