my iPhone 13 max does not want to connect to my WIFI network?

VPN usually creates more problems than it solves. Something to think about→Don't use VPN - GITHUB

There are two legitimate purposes for using VPN:

• To allow access to a private network such as a school or business when you are not on site. 
• To allow access outside of a country with a repressive government that has restricted Internet access. (This has suddenly become more important)

Any other use is risky, and can lead to problems like the one discussed in this thread. VPN disguises your location by making you appear to be somewhere else in the world. But you usually can’t control that “somewhere else”, and if it is in a location that an app isn’t approved for the app won’t work. Plus the fact that the provider of the VPN knows everything about you and your location, as well as what sites you access through the VPN. So you are totally dependent on the VPN provider’s honesty. As a start, if the VPN is free, DON’T USE IT. The provider has to make money somehow, and if you aren’t paying them then they are selling your private data to make money. But even those that charge can’t necessarily be trusted. For example, a few years ago Avast was caught selling user browsing data. They claim they have stopped doing so. 

You don’t really need VPN when using public Wi-Fi, because all communications between your device and the servers it accesses are end-to-end encrypted.

If you want VPN for privacy about the sites you visit, that’s not a good choice as discussed; instead you should download and use the TOR browser.

With iOS 15.2 for iOS/iPadOS and MacOS Monterey 12.2 and later Apple now has iCloud+ Private Relay, which is like a super VPN, except that it doesn't spy on you→About iCloud Private Relay - Apple Support

Well, there are at least a dozen possibilities. But let’s start with some basic ones:

• Does it connect to other Wi-Fi networks? If it does, the problem isn’t the phone.
• First step: Restart your router by removing all power from it for about 15 seconds. Even if other devices connect OK.
• What is the symptom of not connecting? What message do you see when you try?

• Tap the Settings icon
• Tap Cellular
• Scroll all the way to the bottom
• Look just below the last app in the list of apps

Go to Settings/Cellular and turn off Wi-Fi Assist. If on it will switch to cellular if your Wi-Fi speed is slow or unreliable.