IP2Location geolocation service to lookup a visitor's location in Matomo (Piwik) 4.x, 5.x. This service allows you to determine the country, region, city, coordinates, zip code, time zone, ISP, domain, MCC, MNC, mobile brand name, elevation, usage type, address type, IAB category, and more, associated with any given IP address.
In our case we needed to update the function call from
$regionCode = $this->getRegionCode(strtoupper($countryCode), $regionName);
to
$regionCode = $this->getRegionCode(strtoupper($countryCode), strtoupper($regionName));
otherwise the regions were not displayed.
Maybe one can check and make a Pull request for this :)