Prius Radio Problem

It is true that by international agreement there are differences in radio frequencies. This is to reduce or eliminate interference and facilitate proper frequency management. I am certainly not an authority on said agreements or knowledgeable on what is used where. The fact that your radio worked perfectly fine one day and not the next might be pointing to some other problem. Two things come to mind. The easiest is to check the external antenna mounting for corrosion. It unscrews from the mount with the first few turns being indexed to keep the antenna from loosening by itself. If there is rust, clean the threads as best you can and coat with a dielectric grease. The next possibility would be the 12V battery, which when low or discharged will cause all sorts of electrical problems in the car. You can check that yourself, following the plethora of guidance on the subject here in PC, or take it to a mechanic of your choice for a load test.