According to Intuit, error code 1720 is an error that occurs when installing Time Tracker Outlook because a WMI script required to install Time Tracker Outlook was interrupted.
WMI is Microsoft’s Windows Management Instrumentation, a technology through which most Windows resources are managed.
The solution, according to Intuit, is to re-register all WMI .dll files, as discussed in this Microsoft article.
Microsoft has a WMI Diagnosis Utility to help diagnose WMI problems, and it recommends you run this utility prior to making any changes to your WMI configuration.
For more information on this error code, consult this Intuit knowledge base article.