Partitial connevtivity issue ipv6 only couldn't resolve hostname

Hello,

I just started with Cloudflare (Free) and i get the following message on our website monitoring website (updown.io) we use. “partitial connevtivity issue ipv6 only couldn’t resolve hostname”.

All websites are using the cloudflare nameservers.

Can anyone tell me what this means and what i can do to resolve this?