It sounds like the communication settings are incorrect or the configuration folder may have moved or changed. Please try to do the following instructions below to clear the application data which is basically a hard reset for SignCut.
This will reset SignCut so you will lose your cutting plotter settings in the program. If you aren't sure what settings to use and are able to start SignCut, I recommend you to click "Cutter" in the settings menu and write down what you have selected for manufacturer, cutter, output device, and baud.
Please close SignCut then follow these steps to clear the app data.
Windows
1. Open any folder on your computer.
2. Type %appdata% into the address field and hit enter.
3. Locate the SignCut 2 folder and delete it.
4. Restart SignCut and click next then finish and re-enter your cutter settings.
5. Close the program then restart it and all the information you entered should be saved in the program.
Mac
1. Open Finder.
2. Click on "Go to folder" in the Go Menu.
3. Write ~/library in the box and click Go.
4. Open the Application Support folder.
5. Locate the SignCut 2 folder and delete it.
6. Restart SignCut, click Next then Finish and re-enter your cutter settings.
7. Close the program then restart it and all the information you entered should be saved in the program.