Let's refresh your QBO to get the invoicing tab working again, venus _41.
Start with clicking the Reload option beside the QBO URL. You can also press CTRL+F5 to do this. Once done, close and reopen the browser to start from a clean slate.
If you're still unable to open this tab, kindly check if you can do this using a private browser. If it works there, go back to the previous browser and clear the cache. You can also open QBO on other browsers, so I'd suggest switching there.
Please update me with the results by leaving a reply. I'll be here to help you further.