mn100 Tacktick wind not reading on display

[funandadventure]

We bought our boat used which came with instruments ('92). All work fine except for wind. Previous owner said he could never get a good read so stopped using it. Our first year we cruised without it. Now that we are getting ready to launch we thought we would investigate its use. We cannot get the display to read the wind instrument. I can turn on the display and change through the chapters and pages but it is not picking up a signal.
We are testing it on land not mounted to mast head yet so distance is not the issue. Both units have been in sunshine to charge. Display shows fully charged. We have manually spun the cups on the transmitter as well as held them in the wind but no reading. We do not have a manual. Is there a calibration or is something just not right and with its age is it worth having looked at. Replacement pricey. Thanks for your help.