u/Kool-Aid-Women33

I recently got a job offer and the salary was under the employer provided salary range on the job posting. I figured they were anticipating me to counter, so I did with
my desired salary - the same salary expectations I put on my application and within the range listed. They came back and said the salary is not negotiable.

Do I try to counter with something else? (more PTO, bonus, etc) Is this a huge red flag? Help!