Have you made sure that the Integrity Server is configured to allow API connections? I think it's covered under the Integration Builder's Guide but to make sure, you should go to <Integrity Server Install>\config\client\IntegrityclientSite.rc and ensure that the following line is uncommented:
daemon.connectionPolicy=mks.ic.common.policy.ICAllowAllConnectionPolicy
And make sure this line is commented-out:
#daemon.connectionPolicy=mks.ic.common.policy.ICAllowSpecificConnectionPolicy
The Integrity Server service would need to be restarted for these changes to take effect.