If you have upgraded an Apple operating system to Yosemite (latest OS as of this writing), it may render Artisan inoperable because of Java not being on the latest version released for Macs. If so, make sure you close Artisan and get the update directly from Apple at this link http://support.apple.com/kb/DL1572 .
Once you download the update, install it and then try Artisan POS 4 again. It should work fine. If not, contact our technical support department.