Hello there, eurostoneandtile.
This unusual behavior might have something to do with a browser issue. Our browser might be having too much cache that made QuickBooks features not to respond properly.
If you haven't tried logging in to a private widow, we can try creating a sales receipt and invoice and add an item by following these troubleshooting steps. Here's how:
Aside from that, you can use other compatible browsers in QuickBooks Online:
Here are some articles that you can check for additional information about handling sales transactions in QBO:
If you've got an error in the process, please let me know by commenting below. I'm right here to assist you further. Take care always.