I'm glad to have you here, @jrmnork. We know that this isn't a usual thing on your end; not being able to view the Vendor Center functions. Let me share some insights and a workaround to fix it.
QuickBooks Desktop QBDT) Pro 2020 is a discontinued product of QuickBooks. This might be a software issue since the update is no longer available on this version. Furthermore, Vendor Center is still accessible in the latest versions.
In the meantime, we can perform the verify and rebuild to find the most common issues in your QBDT. Feel free to read this article for the detailed steps: Verify and Rebuild Data in QuickBooks Desktop.
Additionally, we'll share these articles for future help:
Please leave a reply below if you have more questions. We'll be more than happy to assist you. Keep safe, and thanks again for coming here.