Sorry this answer has been long overdue but I've fixed the problem. it was the fan that was bad and the used one that i got was also bad.
I used the schematics to check all the connections apart from the MOSFET itslef since the fan did spin albeit on the slowest speed so it does work.
these are the checks i made using the schematics:
``PP1V8_G3S rail to resistors R6050/R6055.``
``SMC_FAN_1_PWM to Q6050 MOSFET.``
``SMC_FAN_1_TACH to R6050/R6055.``
R6050 resistance to pp1v8 reads 49K-50K
R6055 resistance to pp1v8 reads 48K-49K
here is simple connection diagram for the circuit:
``PP1V8_G3S``
``│``
``┌────────┴────────┐``
``│ │``
``R6050 (47 kΩ) R6055 (47 kΩ)``
``│ │``
``└────────┬────────┘``
``│``
``FAN_RT_TACH``
``│``
``────────────┴───────────▶ SMC_FAN_1_TACH``
``SMC_FAN_1_PWM``
``│``
``R6052 (100 kΩ to GND)``
``│``
``GND``
``│``
``┌──────┴──────┐``
``│ Gate Q6050 │``
``│ │``
``Q6050 (N‑FET DMN32D2LFB4)``
``│ │``
``Drain│ │Source``
``│ │``
``FAN_RT_PWM GND``