When processing a sales receipt, I get an error that says "metadata not defined" so I cant process any orders - this worked fine this morning - any ideas?

This can be caused by a browser-related issue, beth_cinquaincel.

We can fix this by logging into our QuickBooks account using a private window. There are times that the browser is full of data files that are causing the unusual responses within QBO.

You can use these keyboard shortcuts:

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

If you're able to process sales receipts without getting the error, I'd suggest clearing your browser's cache. This helps refresh the system and also to function more efficiently.

You can also use a different browser that works best with QBO. 

Please tag me directly if you need more help.