Mom use to do some things herself, now just sits and watches tv. How do I get her to be more active?

Involve her in daily tasks. For example, if she loved to bake or cook do it together. Ask for her help with the simplest task if cooking us difficult. She might be able to wash potatoes or stir something. Even going thru recipes and having her pick out one for you to make brings value.
I always ask my mom for help. She cant do much, but when I do laundry. I ask her to help fold. Who cares if she doesnt do it well, she just feels apary of something. Good luck!

I noticed on your profile your mom has Parkinson’s disease. My mom does too.

They struggle with movements. I’m sure you know this. With my mom there is always a fear of falling. She did fall many times. Their brains say they can move but their bodies have trouble with the movements. It’s a terrible disease.

Is your mom using a walker? Mine is. There comes a time when a cane won’t be adequate.

You will not be able to convince her to be more active.

This is dementia.

If it’s a sudden change it would be best to get her checked by her doctor. There can be a number of reasons why the sudden change.

Equally if its just that shes gradually deteriorated it might be best to get her checked,

Once you know or have eliminated any medical causes then you can follow through with a plan