I'll help you pay your VAT within your QuickBooks Online account, like before.
First, press F5 on your keyboard or click the Reload icon to refresh your account. Then, let's login using an incognito window to test if the problem is browser-related. Here are the shortcut key's you can follow depending on the browser you're using:
Google Chrome: Ctrl + Shift + N
Microsoft Edge: Ctrl + Shift + P
Firefox: Ctrl + Shift + P
Safari: Command + Shift + N
Using incognito mode helps your use QuickBooks without experiencing unusual behavior since there are no history files saved on the device that's causing QuickBooks not to work properly. If it works, we can go back to our main browser and clear the cache. This is to start your data fresh and help QuickBooks to display features and other options.
Also, you can use other compatible browsers like Mozilla, Google Chrome, Microsoft Edge, and Safari. For Safari, make sure to use the latest one. Then, here's how to pay or submit your VAT:
Go to Taxes on the left panel.
Select the Vat tab. Find the return and click Prepare return.