Verbiage on Unclaimed GMB pages: "Own this business?" (KP) / "Claim this business" (Maps) vs. "Manage this listing"

[NiQ]

I have Site Manager access on a GMB page and need to have at least Management to make updates to the info. I'd like at least Ownership to clean up the users though. I asked for higher clearance 30 days ago and have heard nothing back. The Primary Owner of the GMB isn't the business owner anymore. How can I appeal for Ownership?

Your question is a bit vague about the whole situation, but in general -
I think the only avenue you have - is to get in touch with the current GMB owner and make necessary arrangements.
It sounds as if this is the only person with the role of an 'owner', which is the only role that can bring in a new user (including a secondary owner).
There may be some other mechanisms for you to effectively take away a claim of a listing from an existing listing owner, but I would think that this will be a bit tricky, to say the least ...
Basically, you will have to prove to Google that you are the owner, or one of the owners.