There's so much good advice on here. And some terrible advice too!
It may be better to post on the SEN boards in future.
I have an older child who can be a 'school refuser'. No diagnosis as yet but I'm sure its asd probably also adhd. (I work in SEN and older child has their diagnosis.)
Overall (but not always), the main influence on things working or not is my approach. I have to do things differently and recognise the fact it's a nervous system overload not a naughty child.
People who haven't seen the absolute state of my child when she's distressed would not believe me. She's an absolutely model student, so chatty and friendly in my friend groups etc. People who have never dealt with this don't get it at all.
I've had to change my job and hours to manage and I've had to parent differently. There have been days of absolute refusal and days when we've gone in late. Thankfully, all my work places have been supportive and I've been able to juggle things but it's hard. And it's also hard on my child who feels so guilty for causing the disruption but just cannot think clearly enough to move past it at that time. We always talk about it afterwards but it's not a choice. I've had to think about different routines, reminders and strategies to mitigate the feelings of overwhelm.
I just wanted to say, you're not alone. It's tough but hang in there. And even if they refuse now and again, its not a guarantee that they'll refuse outright and you'll never get them in again. Be kind to yourself and if you cry, cry. It's a lot of difficult feelings and you are trying to solve everything in one go.
I hope you're OK.