Transmitter not working

my unit tells me to insert fresh batteries into the outside sending unit first. then insert new batteries into the inside receiving unit. after the outside temperature shows up, then can reset my inside unit's time, choose F or C and
switch channels. please try changing channels if your
outside temp doesn't show. you can do both units in the house then put one outside after they work properly.

Sometimes, you have to remove all the batteries in the transmitter and receiver and wait a few minutes before the next step.

Then you replace transmitter batteries first and within 30 seconds, get the batteries installed in the receiver. This allows the receiver to link up with your transmitter. Both units need to be reset this way. You'll see the temperature and any other information the transmitter provides come up in a few minutes. This works with my La Crosse weather station. Using the reset buttons without removing power will not work. My nieghbour has a weather station from another manufacturer and this is also the only way that his will link up.

I expect that since the unit reads the outside temperature from the remote thermostat, there is no need to "reset" the displayed number since this data is obtained live from the thermostat.

Sure you did put in a new battery? sure you did insert it correct? not the other way around? sure you did use the correct battery? like CR23 or AAA?
Sure all contacts in the battery compartment and on the battery are clean and shiny?
just a few things you could check.

If your outside temperature is not showing on your clock, that may mean that the clock and the transmitter have lost their connection. To reconnect them you must first take the batteries out of both of the units for 15 minutes. First put the batteries back into the transmitter, and then the clock. Let them sit side by side inside your home. When both the indoor and outdoor temperatures show on your clock with the same reading, or within two degrees of each other, then you may put your transmitter back outside. Remember to keep the transmitter out of the direct sun in a dry place. Also keep it away from metal, which can affect the readings.

Did you recently change the transmitter/ bought a new one, changed the battery? How did the problem start? Was it sudden or did the receiver die over a period of time?
Is is possible that the receiver is not recognizing the transmitter's signal. Do you have a spare transmitter? Is the spare transmitter also not working? Please give more information.

Sometimes the RF frequency from the outside transmitter loses contact with the clock's frequency ( it has happened to me only twice in 6 years ), and then the outside temp will not show. Simple solution to fix this is: Take down the outside transmitter and the internally mounted clock. Remove batteries from both. Wait about 10 mts. First install batteries in the transmitter, then after about 30 seconds, install batteries in the clock. In about 5 mts, you will find the clock showing the external temp like before.