Hi Riek,
After checking on our end, it looks like there isn't a widespread issue with sending invoices that causes AccountRight to time out and freeze. Since you're experiencing this problem and have already cleared your AccountRight cache, could you try uninstalling and reinstalling your AccountRight software to see if that fixes it? If the issue continues, we'll need more information to investigate further. You can reach out to our support through live chat via the virtual assistant MOCA or create a support ticket via MyAccount.
Cheers,
Princess