I had the same problem just a month ago. ?I was so surprised to see all my sensor’s gone. ?I went to “add” a sensor and it just didn’t seem right. ?Then I recalled what I did before, which was pretty amazing since it was over 2 years ago.

You just start running your train down the track where your sensors are and JMRI starts “populating” the Sensor table. ?You can open the LocoNet Monitor to see them start to show as the train goes along the layout. ?Then you can go to the Sensor table and you will find the sensors with the name that JMRI gives them. ?It will likely have to do with the brand of sensors that you are using. ?Then you can go to “edit” on those individual sensors and rename them if you wish to be more specific in identifying them. ?

The next step will then be to assign those sensors to your blocks table. ?You will need to go to “add” at the bottom of that table if they were lost. ?Remember the spelling and capitalization of the titles of sensors and blocks need to be absolutely the same.