You have probably tried a cracked license code found somewhere in Internet, and this enforced our cracking protection system. If this is not the case, please contact support to investigate the issue.
Switch back to the valid demo mode using the menu Resize Sense -> Unregister Resize Sense. After purchasing a valid license, register using the menu Resize Sense -> Register Resize Sense
It has been reported that transparent PNG files saved with the
Save As… command by Photoshop CC might not be handled properly by the OS X image import libraries used by Resize Sense. If this happens, please try the Save for Web command in Photoshop instead. This has been reported to solve the issue.