Tricks for getting cat to use litter robot?

I have two cats. One of them is a bit smaller (6lbs) and she took to the LR immediately I hadn't even plugged it in yet and she was already using it (in photo)

My other cat he is double her size. (15lbs) and he is fairly long. I had the LR3 that I bought secondhand he never used it. I was lucky enough to find the LR4 still under warranty (only had for 4 months) on FB market place. I got the LR4 in hopes with its wider opening, he might feel more comfortable going inside. It's easier for me to place him inside to show him that he'll fit, but he still doesn't seem to I want to use it.

Is there anything I can do that might help make him feel more comfortable using it?

I have two cats. One of them is a bit smaller (6lbs) and she took to the LR immediately I hadn't even plugged it in yet and she was already using it (in photo)

My other cat he is double her size. (15lbs) and he is fairly long. I had the LR3 that I bought secondhand he never used it. I was lucky enough to find the LR4 still under warranty (only had for 4 months) on FB market place. I got the LR4 in hopes with its wider opening, he might feel more comfortable going inside. It's easier for me to place him inside to show him that he'll fit, but he still doesn't seem to I want to use it.

Is there anything I can do that might help make him feel more comfortable using it?