Thanks for letting us know, wai-fong,
iOS 16.3 was released this week. We'd suggest that you update the iOS if you haven't already.
What happened when you completed the troubleshooting steps shared from WhatsApp? The link was shared in an earlier message, but you can find the troubleshooting steps here if you need them again: WhatsApp Help Center - Can’t create or restore an iCloud backup
Do you have any VPN software installed on your device? If so, you may consider temporarily removing the VPN as it may interfere with your Internet connection as outlined here: Check VPN (Virtual Private Network) and third-party software to help resolve network connectivity issues - Apple Support
"Check basic settings on your device
Start by checking some basic settings:
- Make sure the date, time, and time zone are set accurately on your device. Learn how to set the date and time on your Mac, iPhone, iPad, or iPod touch.
- Make sure your device's software is up to date. Install any available software updates and then restart your device.
- Restart your modem and router.
- Try switching to another network. If your connectivity issue is resolved by joining a different network, check with your Internet Service Provider (ISP) or network administrator to make sure your network is working properly for the features and apps you want to use.
Check for VPN connections and third-party firewall or security software
Some types of software, including VPN apps or configuration profiles, may have settings or restrictions that can cause connectivity issues. Types of software that could affect connectivity include:
- VPN (Virtual Private Network) apps
- Managed configuration profiles
- Firewall apps
- Anti-virus apps
- Parental control apps
- Content blockers
Review the apps on your device to see if these types of apps or configuration profiles are installed.
On iPhone, iPad, or iPod touch, scroll through your installed apps and check for VPN software or configuration profiles in Settings.
- Settings > General > VPN (even if it says Not Connected)
- Settings > General > Profile (if this option doesn't exist, profiles are not installed)
On Mac, check your Applications folder in the Finder and check for configuration profiles in System Preferences > Profiles.
If any of these types of apps are installed on your device, you may need to delete them to resolve the connectivity issue. Use caution if you choose to do this, since deleting an app or changing a configuration profile could affect how you use your device. For example, if you delete a configuration profile installed by your organization or school, your device may not work with that network.
Use caution if you choose to delete VPN apps or other software
Before you delete any software, you may want to contact the app developer for more information about how the app works with your network, and whether it could cause connectivity issues. For configuration profiles, contact the system administrator for the organization or school that asked you to install it.
On iPhone, iPad and iPod touch: Learn how to delete apps and configuration profiles. If you delete VPN, security or networking apps, also reset your device's network settings.
On Mac: Learn how to delete apps and configuration profiles. If you delete VPN, security or networking apps, you may need to take additional steps. Work with the software developer to fully uninstall their software. Then restart your Mac.
Third-party software might have a subscription to access certain features or services. If you don’t plan to keep using the software, make sure to cancel your subscription.
More help
These resources might be helpful if you're having trouble with a specific feature or setting.
If you're still having trouble connecting, contact Apple support."
Kind regards.
