QuickBooks Desktop for the first time or installing the latest updates, there are chances that error 1721 might cross your path. This mainly happens due to a windows registry error or outdated windows update. If you need help with this error, dial-up QuickBooks desktop support phone number (+1(866)511-4911) and get help from the experts right away. You can also fix this issue on your own with these solutions which are given in this blog.