Reporting temperature 78.4 degrees for 4 days now.
Connie the first thing you need to do is to post the model number or numbers of the system you are talking about. Some of these units will continue to show the last reading they received when they stopped working and others will show dashes. Maybe your sensor just needs batteries.
Ok Connie here are a couple of things, first you could remove the batteries from the sensor for several minutes to see if the sensor will reset. Second the sensor in your 5 in 1 may be bad if its not to old it is user replaceable check this link to see if it fits your unit https://www.acurite.com/temperature-and-humidity-sensor-replacement-for-5-in-1-weather-sensors.html good luck.