When syncing on the PC, you receive the message: "Syncing failed. Error: The user: {ACT NAME} failed to log on to the ACT! database: {DATABASE NAME}. The error is: Logon Failed - Exception is:\{PCNAME}{DB NAME}-database files".

The problem here is that you have installed Handheld Contact to a local machine and not onto the same computer where the ACT! database resides.  This is more often on a server and you have installed locally to your own PC. 

To correct it, you will want to uninstall Handheld Contact from your computer and re-install onto the server directly. The correct server name will be indicated by the {PCNAME} tag given in the error message.  Once you install here, the ACT! database will be found locally and there should not be any issues when syncing.

Note:  This may also be resolved by adding a login to the HHC7Service.  Please see this LINK for more directions.