It looks like you want to see if a string contains at least a capital case character, a small case character, a digit, a special character and if the string is between 10 to 15 characters long.
Like @Toto already commented, I think you flavour does not support lookahead. You can do it without (I borrowed and enhanced the code from here) by using capture groups and test them:
^
(?> #MAIN iteration (atomic only for efficiency)
(?<upper>[A-Z]) # an uppercase letter
| # or
(?<lower>[a-z]) # a lowercase letter
| # or
(?<digit>[0-9]) # a digit
| # or
(?<special>[^(0-9|a-z|A-Z)]) # a special
| # or
. # anything else
){10,15}? #REPEATED 10 to 15 times
#
#CONDITIONS:
(?(upper) # 1. There must be at least 1 uppercase
(?(lower) # 2. If (1), there must be 1 lowercase
(?(digit) # 3. If (2), there must be 1 digit
(?(special) # 4. If (3) there must be 1 special
| (?!) # Else fail
) #
| (?!) # Else fail
) #
| (?!) # Else fail
) #
| (?!) # Else fail
) $ #
You can test it here: regex101 example