How to make him jump in!

Backstory: when we first got this lil guy (now 3.5 years old), we had a 14 year old with cancer and arthritis. She couldn’t jump anymore so she would put up her front paws to “help” and then we’d lift her back end up for her. Bowser here learned that trait from his sister and we didn’t discourage it because when he tried to jump so did she, and she once got hurt trying before we could stop her. After she passed almost two years ago, I guess it was just habit for all of us. We kept doing it. Now he absolutely refuses to jump in.

Unfortunately I’m having some medical problems of my own and I can’t keep lifting him. He’s definitely capable…He can jump four feet in the air for a frisbee! He’s also done it to chase our son in.

He’s terrified of the steps we had for our old dog and I assume ramps will have a similar reaction. And we’ve tried treats…so many treats! And we’ve also tried from the wide open trunk.

TL;DR How do we unlearn this behavior of 3.5 years and get the cute little booger to jump like I know he can? Tips? Tricks? Thoughts?

Backstory: when we first got this lil guy (now 3.5 years old), we had a 14 year old with cancer and arthritis. She couldn’t jump anymore so she would put up her front paws to “help” and then we’d lift her back end up for her. Bowser here learned that trait from his sister and we didn’t discourage it because when he tried to jump so did she, and she once got hurt trying before we could stop her. After she passed almost two years ago, I guess it was just habit for all of us. We kept doing it. Now he absolutely refuses to jump in.

Unfortunately I’m having some medical problems of my own and I can’t keep lifting him. He’s definitely capable…He can jump four feet in the air for a frisbee! He’s also done it to chase our son in.

He’s terrified of the steps we had for our old dog and I assume ramps will have a similar reaction. And we’ve tried treats…so many treats! And we’ve also tried from the wide open trunk.

TL;DR How do we unlearn this behavior of 3.5 years and get the cute little booger to jump like I know he can? Tips? Tricks? Thoughts?