IOS 16.5.1

Are you using a captive WiFi?

If your device doesn't automatically join a captive Wi-Fi network:

• Tap Settings > Wi-Fi.
• Tap the More Info button next to the network name.
• Make sure that Auto-Join is on.

Use captive Wi-Fi networks on your iPhone or iPad

Your device is probably not connected to the internet. There are a few steps you can take to verify the connectivity of your device.

Firstly, you can open a web browser on your device. When you open a web browser, the initial page that loads is typically based on your browsing history or cookies. To further confirm the connection, you can tap on any link on that website. If the link opens and displays the corresponding content, it confirms that your device is indeed connected to the internet.

Another method to check internet connectivity is by opening a specific application that requires an internet connection. WhatsApp is an example of such an application. When you launch WhatsApp, it immediately attempts to establish a connection with its servers to synchronize your chats and display any new messages. If you can see your chat conversations and receive real-time updates, it indicates that your device is connected to the internet.

Connecting to Wi-Fi is the initial step, followed by establishing an internet connection.

However, it's important to note that connecting to Wi-Fi does not automatically guarantee an internet connection. In the event that you are unable to connect to Wi-Fi, the issue may stem from settings on your iPhone or the router/modem.

On the other hand, if you are unable to establish an internet connection despite being connected to Wi-Fi, the problem is likely related to the settings on your router/modem. In such cases, it is advisable to promptly contact your Internet Service Provider (ISP) for assistance.

Check your WiFi Router / Modem for --> Recommended settings for Wi-Fi routers and access points ...

For your Internet connection.

• Over Cellular: contact your Carrier (Cellular Service Provider). The agency that issued the SIM to you
• Over WiFI: Contact your ISP (Internet Service Provider), the agency that provided the Internet Service on your Modem/Router to you

However --> Connect iPhone to the Internet - Apple Support

Updating iOS on your iPhone should not change your personal details. iOS updates primarily focus on improving system performance, introducing new features, fixing bugs, and enhancing security. They are designed to preserve your personal data, settings, and information intact.

During an iOS update, your device's operating system is upgraded, but your personal data, such as contacts, photos, messages, and other information, should remain unchanged. However, it's always a good practice to perform a backup of your device before any major update to ensure that your data is safely stored.

It's important to note that while an iOS update itself should not alter personal details, it's possible that certain features or settings may be adjusted or improved with the update. In such cases, you may need to review and adjust specific settings to match your preferences after the update.

Always make sure to read and understand the update details provided by Apple before proceeding with an iOS update, and follow best practices such as backing up your device to minimize any potential risks or complications.

If the issues you mentioned are indeed caused by iOS, it's likely that numerous users who have upgraded to iOS 16.4.1 (a) or 16.5 are experiencing similar problems. However, in order for the community on this forum to provide helpful responses, it would be beneficial for you to specify the nature of the issue you are encountering. Without this information, it may be difficult for others to address your concern effectively.

With the limited information that you have provided, It is hard to even guess the problems faced by you. 

You may get faster and better responses to your query by --> Writing an effective Apple Support Commun… - Apple ...

Please re-post with detail so that someone else can help.