Using https://support.apple.com/en-us/HT200285 to change wallpapers every hour and randomly doesn't function for me. Pls help!

When you say: "Randomly doesn't function" it does not give me any clue as to what the issue is.

Issues on an iPhone are rarely random unless you have not noticed the earlier occurrences. Most problems or malfunctions experienced on an iPhone are not completely unexpected or random. Instead, they often have underlying causes that can be traced back to previous occurrences or signs of trouble that may have been overlooked or unnoticed by the user.

In other words, it implies that iPhones typically exhibit symptoms or warning signs before encountering a major issue. These symptoms may be subtle or minor at first, but if they are ignored or left unaddressed, they can escalate into more significant problems over time.

For example, if your iPhone's battery life has been steadily decreasing over the past few weeks, and you choose to ignore it, you may eventually experience a complete battery failure or sudden shutdown. In this case, the issue is not entirely random because there were earlier occurrences (decreased battery life) that could have indicated a problem.

The underlying idea is that iPhones, like any complex electronic devices, usually give some indications of trouble before experiencing significant issues. It's important for users to be observant and proactive in identifying and addressing these early signs to prevent more severe problems in the future.

Are you asking about the Photo Shuffle feature? If so, I'd suggest turning it off, restarting the phone and then enabling the feature again.

Follow the directions in the article you linked to above. Unselect Photo Wallpaper by choosing something else.