Sure thing! Firstly, ensure all connections are secure and power is supplied to the device. Then, try resetting the OP121 by powering it off for a few minutes and then powering it back on. If the issue persists, check the display for any error codes or abnormal readings. Additionally, review the manual for troubleshooting steps specific to your issue. If all else fails, it might be time to contact Siemens technical support for further assistance.