Whenever I someone says "It didn't work until I turned off #IPv6", I hear "It didn't work until I replaced the fuse with a paperclip." Sure, it turned on, but there's something else amiss in your system that needs to be addressed.
@nivex What you describe as "your system" means anywhere between your browser and the webserver, unfortunately...
My ISP still doesn't support it, and using a tunnel like he.net just makes things like Netflix and Roku stop working. The solution to that is to disable IPv6 on the network. 😞
They've been noncommittal about it every time I've asked, and considering they just went through a bankruptcy I don't have my hopes up.
Their fiber network is still pretty solid or I'd have switched off them by now.
I have IPv6 shut off on the router here because you can't (easily) disable it on individual devices like "smart" TVs, streaming dongles, etc.