My DD has encopresis. Now I'm not saying yours does, but I remember very well the issues of potty training.
Her first problem was holding it & hiding. We soon found out that bec of this she had started to get bowel blockages & it was painful for her so she associated the potty with pain.
We didn't know any of this at that time. Our big mistake was that our pediatrician told us to use a mild laxative then when she'd go, take her off it.
Problem was it started all over again. Looking back we should've kept her on it.

We were told a lot about working reward charts, stickers & short term goals to keep her motivated. Maybe this would help? Like 5 stickers equals cool markers or something etc.

I was told that for a boy, to keep them motivated to go was to let them put cheerios in the toilet & then try to aim for them. Funny!

Keep it very light. No pressure & stick with that routine of going & trying. Yes just a few minutes to try & then a reward.
So what would motivate your child? That's the big question. Something they REALLY want. They can see or touch.

I hope you find something that helps. So you have a year to work or this for kindergarten or does your child start in September?