Hi,
I'm Sumit, here to help with your query on the Microsoft Q&A forums.
Apologies for any inconvenience you are experiencing. I am happy to help you today.
I have personally published an Edge extension to the Store as well. I am wondering if your URL is correct i.e. https://partner.microsoft.com/en-us/dashboard/microsoftedge
If so, please share a screenshot of the error.
I look forward to your response and am eager to collaborate until we find a solution.