It's possible to run into the QuickBooks error 15101 during or after a payroll or software upgrade. The message lets you know that QuickBooks Desktop failed to update, and it stops you from performing your financial tasks on the QuickBooks software. The most frequent reasons of this error include incorrect internet settings and problems with defective digital signature certificates. However, there may be other reasons as well, which we shall learn in this article. By the end of this article, we will make sure that you are able to fix QuickBooks Error code 15101.