They say that my POA doesn't mean anything. Advice?

I am Mom's caregiver. I have POA and get paid to care for her. We live in a home here in florida. They say that i need a 3rd party to sign my time sheets. I have POA. They say That i cant sign them if mom has dementia. I have sold her home and burried my father. I think they are wrong but i cant prove it to them. I should be able to sign for her. they say no. i cant sign my own time sheet.