Invalid expression is get generated

[KamranShahid]

What i wanted is
"The Password must have a minimum/maximum of 8 characters, including 1 special character, 1 digit and once capital letter."
I have a following expression ^((?=.\d)(?=.[A-Z])(?=.*\W).{8,8})$
But it is not generating valid string as per my requirement
Please check what's the problem

[(https://stackoverflow.com/questions/57006786/not-able-to-generate-string-from-complex-regular-expression-with-fare)]