Guided Access not starting on my iPhone 15 Pro Max when triple-clicking

So I recently started using Guided Access on this other iPhone I have. I have it turned on my iPhone as well. I just let my kid use it to watch videos on YouTube kids. So I like to lock down the phone so she’s not able to call and go on other apps and stuff. I have problems with Guided Access turning on. Occasionally, it’ll work on the other phone, iPhone 14+. It hasn’t worked on my phone. My phone is iPhone 15 Pro Max. Every time I triple click on YouTube as an example or any streaming app it doesn’t even start. Guided Access doesn’t do anything. I have restarted my phone. I have turned off Guided Access and turned it back on. Both phones don’t always start guided access when you triple click. I wish there was another way to enable guided access instead of triple clicking. Siri won’t turn it on

[Re-Titled by Moderator]