What advise would you give to clients that are married and not getting enough sex at home and desire to have more sex with SO?
I would suggest romance her, talk to her, see what your SO is desiring or missing to be in the mood with you.
There are many reasons someone may not be in the mood.
Hormones, feeling over worked, feeling taken advantage of, feeling undesired, then there can be sexual disconnect, not on the same page for desires, incompatible expectations in the bedroom, unappreciated, sex feeling like a chore because she isn't feeling pleasure i the exchange... ect. The list goes on what the problem/s can be. It just often as humans it is easier to sit back and blame the other person, rather than look at how we can do our own part in correcting the issues.
And it's more than just talk, but actually correcting issues. Complaining she isn't putting out isn't going to help, and only make sex a chore to her, but to find out what will get her to want it from you is golden. A relationship is an active work over time to keep it alive, by both parties involved. When either stops trying, it's only a matter of time before both stop trying.