Welcome to Community! Not having the ability to see your supplier details in QuickBooks Online is definitely concerning. I'd be glad to assist!
If you haven't done so already, I recommend clearing cache on your browser, to improve system performance and loading times. If you get the same result, please try another browser such as Safari, Edge, Firefox, Google Chrome, or a private/incognito window. Should you experience the same outcome, contact us outside of Community, so we can review the unexpected behavior in more depth from our end, and ensure you're back to business as soon as possible!
Schedule a Callback or start a Chat: click (?) Help in the upper right in QuickBooks Online > enter "Contact support" > hit Contact Us > provide a brief summary of your situation > hit Let's Talk > choose Get a callback or Start a Chat.