This behavior happens when accumulated cache data disrupts the system’s functionality. To isolate this, attempt to save your invoice using an incognito window.
If it saves correctly, let’s clear your browser’s cache to remove the temporary data causing this issue.
If you’re using Chrome:
Navigate to the three vertical dots at the top right corner of your browser.
Select Delete browsing data.
In the time range dropdown, select All time.
Select the types of information you want to remove