Syncing my laptop premium prescription to my iPhone

Hi, I have a premium prescription.   Yesterday I had problems with the stock screening function on the iPhone... the pages would uncontrollably scroll to the right.   So, this morning I deleted the app on the IPhone and downloaded it again.   I can sign in, but it doesn't respond with my username nor allow me to sign into premium without paying the premium prescription.   There must be some issue with syncing the laptop to the iPhone so I can access the premium prescription on both.  What do you suggest?