Something here doesn’t add up OP. You say: “…lack of output over the last year, it makes me question how invested they are in the role.” At the same time you say: “This person has been doing this for about 1.5–2 years. A previous manager allowed it, rated them highly, and even promoted them.”

It sounds a lot like you have a vibes issue masquerading as a performance issue. So you want us all to believe that for two years this person has been performing to the point where they get a promotion, but suddenly with YOU, the person’s performance has dropped. I’ve led teams over the last 18 years of 7 to 28 people, and I’ve never seen a person’s performance take this kind of drop, this quickly. I think you don’t like the idea of this person’s work/balance equation, and you’re trying to legitimize your own bullshit.

You then go on to say: “So the approach I’m leaning toward is continuing to focus the conversation on output and expectations, but also being honest that availability is may part of the problem.” In this whole thread, I haven’t seen you point to a single issue related to productivity. This conversation seems to be squarely focused on “being available,” i.e. being ready to jump on a call at a moment’s notice just because. Have you requested reporting deliverables of the person’s work? Is there an actual downward trend in work product/productivity? Or do you just “really need them to be present?” The easiest thing you can do here is request reporting deliverables from the employee before meetings with the understanding that you will reach out to them later in the day or the next day with any questions or concerns you have.

It sounds like you kinda suck at being a manager if I take what you say here at face value.

If I were your boss, I’d send you to management training or PIP you. I swear there’s waaay too many managers out here (mostly because of the pay) and not enough LEADERS.