CF2018 - cflogin or cfthread logging user out

I upgraded to CF2018 from CF2016, running on a Windows 2016 Server with IIS. I am using subdomains.  Example: A user logs into app.mydomain.com using cflogin and they click a button to create a batch of work to do.  The button click launches an ajax remote call to job.mydomain.com to setup a job queue in the database sets a task in the CF Scheduler.

The scheduler launches the job page on job.mydomain.com that queries the job info.  It knows what subdomain it was from and what user created it, so within a cfthread it executes a remote call to app.mydomain.com and does a cflogin allowconcurrent=true for the userid that was sent.  This way it can know the permissions and whether this user can process it.

In CF 2016 it works great.  Upon upgrading to CF 2018 it logs the user out as soon as the scheduler runs and does the cflogin within the thread.

Does anyone have any idea what might have changed from 2016 to 2018 that may have broken this?  Or any ideas how I can implement so it will work again?