QuickBooks Error Code 15101 refers to the occurrence of connectivity failure. This can occur, either when you are not able to connect to the internet or when QuickBooks is not able to access secured websites. As the there are a series of errors that fall under 15*** patterns, thus there are multiple reasons for the occurrence of the error. Hence the solutions are also different. You do not have to perform all the solutions. For the specific error message follow the solution accordingly. You can also refer to the knowledgebase for instructions on how to resolve any particular error starting with 15***.