It is most likely that your IPTV provider blocks VPN access and haven't discovered all of PIA's IPs yet. Depending on which region you connect to and which IP address you get, you can be lucky that your provider haven't found it yet or be unlucky and it is blocked.
What is your IPTV provider and are they known to restrict access to specific countries or regions?
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What is your IPTV provider and are they known to restrict access to specific countries or regions?