unable to crack scrypt digest

Hi,

I am trying to crack scrypt digests. I am creating my own digests using the python library pyscrypt for that.

the python script:
b64encode(pyscrypt.hash(password="hashcat", salt="salt", N=1024,r=1,p=1,dkLen=32))

which gives:
'oDLxfd3z2gOBjdQMAy9M+uSzGiLwOlNwmSgLSihkgm8='

my cudaHashcat command on my windows machine is:

cudaHashcat64.exe -m8900 SCRYPT:1024:1:1alt:oDLxfd3z2gOBjdQMAy9M+uSzGiLwOlNwmSgLSihkgm8= rockyou.t
xt

result:
the crack is exhausted even though I have added 'hashcat' to the rockyou.txt dictionary

P.S. I was able to successfully crack the SCRYPT example shown on the hashcat hash examples page

Could some one please tell me why my digest don't crack