Breakers in the panels are OK

Did you actually turn them fully off and back on again? Some breakers don't look 'popped' even though they are.

Are there any GFCIs outside of the house? Do the outlets outside work?

I was going to say the exact same thing, physically flip the breaker switches, often times you can't tell just by looking at them. I am sure a pro could find the problem quickly.

Thanks - I've never seen a breaker that didn't physically flip when triggered, but tried all 54 of them individually, with no success. I haven't spotted any outdoor GFIs but on testing those outlets it looks like at least some of them are out - so at least it's making more sense. I'm thinking there has to be one outside or one in the garage we can't find.

Turns out the "just keep looking" tact was key - finally found the culprit - one little red button and it's fixed! Thanks again for the helpful posts.