OPOS drivers need exclusive use of the port. If you are using OPOS drivers, check to make sure no other printer drivers are set to use the same port.
Example: If you have a parallel receipt printer using LPT1:, make sure no other printer driver listed under Control Panel, Printers and Faxs is set to use that port. If it is, remove the driver or change the port setting to another port (such as LPT2:). Exist POS if already running and return.
If this does not resolve the problem, you may need to update your OPOS driver or configure the registry settings for OLE for Point-of-Sale (OPOS) in Windows. Contact our support team for further assistance.