Radios can malfunction if the antenna is loose, or if it's the wrong type, or installed incorrectly.
Start by removing the antenna by turning in a counterclockwise direction. Look to ensure you have the correct antenna type for your radio — the standard whip antenna, which is long and thin, or the stubby antenna, which is much shorter. The antenna will have either a pin or a flat connector; look at the connector base on the radio and make sure it's the correct shape to fit the connector, pin or flat. Also look at the antenna and see whether it has "UHF" or "VHF printed on it. Look at the model number on the radio label, and check the documentation for that radio to see if you should be using it on the UHF or VHF frequency band; make sure you have the appropriate type of antenna for that frequency band. If you appear to have the correct type of antenna, reinstall it by turning it in a clockwise direction and turn the radio back on.
These batteries usually last between 18 and 24 months depending on the amount of usage. You can check the manufacturer's date of your battery by first removing it from the radio and checking the four digit number located on the back of the battery next to the bar code; the first two numbers indicate the year and the second two numbers indicate the week. If the batter is over 24 months old, replace it.
If your radio has a display screen, you can check its battery life as indicated on the top left corner of the screen. If there's no display, when turning on the radio, you can listen for a double beep being emitted from the radio. This is the indicator of a low battery.
You can also check the LED light indicator on the radio's charger. If your radio doesn't seem to be turning on, place it securely in the charger, making sure the contacts of the battery align with the contacts of the charger. Look at the LED light and note what colors are displaying and in what pattern.
It can be helpful to try a battery swap: take a battery from a functioning radio of the same type, and insert it into the malfunctioning radio. If this resolves the issue, changes are you need a new battery.
If you have a bank of emergency radios, check their batteries on a monthly basis to make sure they're charged and the radios are working properly.
TIf accessories such as remote speaker mics or two-way surveillance kits are not working properly, first try powering off the radio. Remove the accessory, resecure it, and turn on the radio. (Always follow these steps when attaching the accessory.) Does the radio register the accessory on its display when it's attached?
Try turning off the radio, removing the accessory, and cleaning the contacts on the radio with a pencil eraser to take off any residue. After cleaning, with the radio still off, reattach the accessory and turn the radio back on. If this doesn't fix the problem, try turning off the radio and swapping in a new accessory — if that one registers, then it's most likely the accessory itself that's malfunctioning.