When the error occurs to protect your computer and its crucial contents, QuickBooks tries to verify the digital signature on all files that are downloaded through the program. If QuickBooks is unable to verify the digital signature of a file that you are trying to download, one of these errors will occur.
On having encountered the issue, to fix this error, you need to download the latest version of Internet Explorer from the Microsoft Download Center.
For the resolution of QuickBooks error 15217, manually download and install the latest QuickBooks update. Once update is done the error will be resolved.
If the above solution does not resolve the issue or answer your question, you can read discussions and post messages and questions relating to your issue on the Intuit QuickBooks Community site introduced by Intuit or you can connect with the QuickBooks Error support for guidance and error fixation.
There are a number of third party file repair companies that can fix this issue instantly.