Our IIA did this:
Drove up to a house to cut the grass. Got ready to leave, engine would not turn over, no click or sound from the starter, nothing. New gel cell battery, so if dead, we had a significant drain on it
. Tried to jump it, could not get a peep (not even a click like yours is doing) out of it. Called my 82yo dad. He said seems like you got a dead spot on your starter". Rock the truck with it in gear and see what happens. Rocked it hard...... several times. Voila! Cranked right up. He told me if it happens a gain to get the starter rebuilt, but it has not.
Just an easy thing to try...... and free.
Greg