If you are unable to print invoices, estimates, etc, or any of your reports, it may be because of the pop-up blocker.
One of the problems that regularly occurs is the inability to print a transaction or a report.
However, this is usually caused by your browser's pop-up blocker.
Disabling the pop-up blocker is different for each browser, and is also dependent on whether or not you're using mobile or desktop.
The following are links to disable the pop-up blocker for common browsers: