This seems to be a common issue lately. I've seen at least four complaints here in the last few days... Not sure the solution, though. Intuit will probably blame your browser.
I'll make sure you can view your vendor list, @Jwipf.
We can perform basic browser troubleshooting to fix the issue. It could be that the stored cache and cookies in the system are the reason why you're having issues accessing vendors.
We can start by accessing your QuickBooks account through a private/incognito browser. Feel free to use these shortcut keys:
Google Chrome: Ctrl + Shift + N
Mozilla Firefox and Microsoft Edge: Ctrl + Shift + P
Safari 11 or newer: ⌘ + Shift + N
Once you're in, let's go to the Expense section to check your vendors. If we're able to view them, we'll need to go back to your regular browser and clear the cache to get rid of the junk files and site data.
If the issue persists, we can use other supported browsers. It could be that the one you're currently using right now has a temporary problem with QuickBooks Online.
I also recommend reading this article to be guided in customizing and managing your vendor profile and transactions: View Vendor Transactions.
I'm always here to help if you have any other concerns or questions. Just tag my name in the comment section and I'll get back to you as soon as I can.