The unit tics the temp sensor upon startup to detect if there is indeed an xducer attached ... If it doesn't detect the temp sensor = the unit gives the "Transducer Not Connected" popup ...
The adapter cable may not be allowing temp data ...
You may have to force the unit into normal operating mode to bypass this startup temp sensor detecting sequence ...
When starting the unit - press the "Menu" button when the HB splash screen appears to get the forced startup options ...
Then choose "Normal Operation" from the popup list ...
Rickie