The App Store is unavailable in the country or region you’re in.

The message "The App Store is unavailable in the country or region you’re in"It appears when we try to open Apple App Store on iPhone, iPad or iPod touch for updates or download applications on devices.
Although many users interpret it as an error, this message appears after some regional limitations to access Apple OR SERVICES.
Apple offers games and applications in the App Store depending on the location you have set iPhone, iPad or iPod Touch during initialization. There are applications such as "News" Apple or Google Assistant that are not available unless you have iPhone set to the USA or UK region. This is a regional limitation on applications and games.
Another limitation is the one on the IP addresses in a region or country. This is what happened recently with all users of iPhone, iPad and iPod Touch from Iran.

This message appears regardless of whether iPhone is set on a region of Asia, Europe or US. The limitation imposed by Apple is valid on all IP addresses in Iran. Due to the sanctions imposed by Iran by the USA, Apple is not allowed to sell services and devices in this country. In Iran there are millions of iPhone users who have purchased their devices from Dubai and Hong Kong markets, and until recently they could access the Apple App Store if they set the devices to another region.

In this situation, the prohibition ""The App Store is unavailable in the country or region you’re in"It can only be avoided if users in Iran connects to the Internet through an VPN (Private internet network) that will go out with IP from an Apple's region / country to access the App Store.