Third-party security software that monitors or interacts with network connections can potentially block some connections, such as those required to access the internet or communicate with other devices on your network.
If VPN (virtual private network) software or other third-party security software has been installed on your device, connectivity issues such as these could be related to that software. As detailed in the linked articles, these issues can also have other causes.
Your device can't connect to the internet, or can't connect to Wi-Fi.
Your device can't back up to iCloud or can't use Time Machine.
Your device can't turn on or sign in to iMessage or FaceTime.
Your device can't connect to other Apple services such as the App Store or iTunes Store.
Your device can't communicate as expected with devices on the network, such as to transfer data, use AirPlay, or use certain other Continuity features.
Make sure that the date, time, and time zone are correct on your device, and learn what to do if you can't change these settings.
Make sure that your device is using the latest software updates.
Restart your device. You might also need to restart your modem and router.
Connect to a different network to find out if the issue is specific to your network. If it is, your internet service provider or network administrator might be able to help. You can also check for Wi-Fi and Bluetooth interference, especially if the issue is intermittent.
These changes could affect connectivity from your device. If your device is managed by your organization or configured for access to their apps and services, you might be unable to make changes and should consult them before proceeding.
If you don't know what VPN or other third-party security software you might be using, check your device for these types of apps. They're available from many different vendors and have many different names. Words like Anti, Alarm, Firewall, Mechanic, Malware, Protection, Security, Shield, Spy, Trust, Virus, or VPN might be part of the name.
VPN apps
Firewall apps
Antivirus apps
Parental-control apps
Content blockers
On iPhone, iPad, Apple TV, or Apple Vision Pro, look for such apps on the Home Screen. On Mac, look for them in the Applications folder and elsewhere in the Finder. To aid your search, you can use Spotlight on iPhone or iPad, use Spotlight on Mac, or use Spotlight on Apple Vision Pro.
If you find any such apps:
Use the app to turn off its features, then see if the issue continues.
If you don't recognize an app or aren't sure how to use it, contact its vendor for more information, or delete the app.
If you subscribe to an app that you want to delete or stop using, cancel your subscription.
Whether or not you're using any of those types of apps, changes might have been made elsewhere in your device's settings. To find out, search within settings for these words: VPN, profile, firewall, and filter.
On iPhone or iPad, open the Settings app, then swipe down to reveal the search field.
On Mac, choose Apple menu > System Settings (or System Preferences), then use the search field in the corner of the window. Check for related login items as well.
On Apple Vision Pro, open the Settings app, then use the Search field at the top of the sidebar.
On Apple TV, open the Settings app, click General, then check for settings in the VPN & Device Management section, if available.
If the setting isn't managed and required by your organization, you can turn it off, change it, or delete it. For example, on iPhone or iPad, you can tap a configuration profile, then tap to confirm that you want to delete it. On Mac, you can select the profile and click the Remove (–) button below it. However, if the software that created the setting is still in use, the setting might return later.
After making changes, restart your device. If the issue continues, reset network settings on your iPhone or iPad or reset network settings on Apple Vision Pro. Then restart and reconnect to your network. On Mac, you can reset network settings by switching to a new network location in Network settings.