Dog nuisance and poop = Member complaints to HOA

A member has complained for years that his neighbor's dogs are a nuisance and that the neighbor has been lax / allowing her dogs to go in his yard to poop.
It has gotten so bad he is asking the board again to intervene and is threatening legal action. I am one of three Board members.
Side point; we only allow two pets per owner, but this member owns three dogs. One she states is a service dog.

She hhas denied the dog poop is from her dogs... it is a 'she said, he said' issue.
Her dogs bark a lot and scratch the walls a lot...
But what as a HOA can we do?

It has escalated to a point where each side has called the police a few times on each other.
She feels harrassed and he feels she is not following the rules and also that the dogs are out of control causing hardship for him.

Thanks.

Thanks for the reply, makes sense.

I agree it's a neighbor v. neighbor issue UNLESS the HOA has rules about dogs being off-leash or doing their business in the yards of others. We certainly have rules against dogs using our common areas, and we certainly do call the owners to hearing if witnessed or seen on camera. Rarely happens but we do enforce this.

As MelissaP1 said.. I think Animal Control can have the solution. But HOA can enact the rule of having only two pets not three.