Is there a problem with quickbooks? I keep getting the error "When you use Accounts Payable, you must choose a supplier in the Name field." despite the name I entered

Warm welcome in the Community, @lebogangmonyela.

These messages appear when the name associated with that account is not a customer or vendor name.  If it's already listed we can perform the troubleshooting steps below.

To isolate this unexpected behavior let's log in to your account using a private browser.  This way, we can determine if this is a cache-related issue.

You can use either of the following shortcut keys:

• Chrome, press CTRL + Shift + N.
• Mozilla Firefox: press CTRL + Shift + P.
• Internet Explorer: press CTRL+ Shift + P.
• Safari: press Command + Shift + N.
   

If it works fine as suggested, you may need to clear the cache of the regular browser you're using. Otherwise, try using other supported browsers. 

For future reference, check this article on how to make and record a journal entry in QuickBooks Online.

Please reply to the comment section below if you need further assistance. I'm happy to help. Take good care!