Just wanted to provide some additional info if it helps. As this is BluePrism University content related issue, you can post your queries in the BluePrism University Community.
I just checked and I can access the Decipher course. Please make sure you have created an account on portal.blueprism.com, followed by login and then access courses on university.
Thank you Tejas and Shashank, I already have account created. I was able to enroll for other courses but not Decipher. However, with the link shared by Shashank, I am able to access the course.