I am not sure if the attached link to Ventline Monitor Panels information (now owned and branded by Dexter), will be of any help to you or not, but there is a section in the information for troubleshooting typical problems with these monitor panels. It might help you to check that your +12vdc and grounds are good to the panel first and then the wiring to the specific sensors and finally the circuit board.
https://www.nroa2003.com/download/Ow...tor-Manual.pdf