No online game ever launched smoothly, and that goes double for Blizzard games. Maybe triple for Diablo given the legacy of old mate Error 37. As Diablo 4 arrives in early access for folks who pre-ordered it, those of us playing on PC have mostly been able to get in easily, with a five-minute queue here and there. The same can't be said for our PlayStation friends.
The unexpected error message "Unable to find a valid license for Diablo IV" has prevented many players from being able to enjoy their early access privileges, and Blizzard has noted the issue, saying, "The team is looking into this right now and will update once we have more information."
Obviously people who put down cash to pre-order Diablo 4 have valid licenses and should be able to log-in. Some players have had success convincing the PlayStation Network of this fact by throwing an extra $1.99 at Blizzard for the smallest bundle of its in-game currency available. As Azule says in the replies to Blizzard's forum post, "you just have to by [sic] in game currency and then it will lwt [sic] you log in… crazy!!"
Which is obviously a ridiculous thing to have to do. Fortunately, other players have found a way around the situation that doesn't cost anything. Downloading a free game like Brawlhalla, a demo, or something from the PSN+ library will remind the console you've actually got a valid license and you should be allowed into Sanctuary to smack some Fallen around after all.