What to do for an unhappy client?

Hi all, So I've just had my first unhappy client and I'm struggling to come up with the best course of action.

I completed a 12 night stay, watching this clients dog and guinea pigs in their home. We had two meet and greets and communicated during their vacation, sent photos, etc. At the end of the stay, I took the guinea pigs home with me to board them while they picked up the dog to go with them on a second part of the vacation.

The next day I was contacted by Rover support and told the client was "unhappy" with the stay and Rover had arranged a new sitter to pick up the guinea pigs. Rover didn't have a reason as to why the client felt this way.

Should I try to find out what happened? I know I took good care of their animals and their house was as good or better than how they left it. They kept tacking on extra housework/animal needs after the booking, and if I'd known everything up front I probably would have declined the stay (it was already way out of my service area). I did everything they asked to the best of my abilities.

Is it wise to contact the owner after they return from vacation to find out what went wrong or should I wait to see if they open a case through Rover? At what point would you offer a partial refund? Does Rover ever refund unhappy clients directly? I hate to lose more money because I way undercharged for the service they ended up getting, but I'd like to avoid a negative review and I do genuinely want them to feel satisfied.

Thanks for your advice