Classroom in a book

I just tried the link in your post and it worked. First it asked me to sign in on the Peachpit/Pearson website, the publisher of Adobe Press books (I already have an account, but if you don’t you might need to create one), and after that it showed me the Register a Product page with the ISBN number of the book already filled in. I didn’t go further but after that the lesson files should be on the book’s web page, usually under a tab named “Lesson & Update Files”.

Were you able to get that far, or when you try, what does the website show you instead?

Make sure that when the address is typed or pasted into the web browser that there are no spaces or extra characters. I copied and pasted what you typed into your post, and that worked in my web browser (Apple Safari).

(Note that this forum is not normally the best place to get answers about the book itself, because Adobe Press is a Peachpit/Pearson imprint, and this forum is about the actual Photoshop software. So questions about the book or its website are best directed to the Product/Tech Support Help contact info on the book website. The only reason I can comment on this question is that I work on other books by that publisher, although I am not the author of Adobe Photoshop and Lightroom Classic for Beginners.)