Hello, have the battery connections been checked, are the clean and free of corrosion and tight, I would remove them, clean them and make sure they are tight first.
If the battery is good as well as all connections and there is a single click noise when turning the key it indicates that voltage is getting to the starter solenoid but the starter won't turn the engine over, in that case it will most likely be necessary to replace it.
The connections are clean and tight. Actually, today the sound made when turning the key is more of a buzzing sound. Prior to that it was a clicking sound. Is the starter likely bad?
It does sound like that's the case.