Remember, the server is checking your IP address as part of the authentication. VPNs generally grant a variable proxy IP address, so your IP address may be different than what was seen before, so you may need to do an IPTV Reset to clear your credentials. I know that some IPTV services may block service to certain countries, I'm pretty sure that the supported services do not do this for the most part, so if you continue to get blocked after doing an IPTV Reset, try a different country.
Something else...your ISP might be actively filtering VPN traffic, especially if you are using it constantly, as it might be in violation of their terms of service. Also, the routing that the VPN is using might be going though a filter point stopping streams.