As i explain in my first post, because i have Windows Server 2008 i am limited to use ACME V1, because of that i use the last letsencrypt version possible that is version 1.9.7
So nothing to do with Certbot because i use a Windows Server not Linux.
About the issue, as you ask i also think this is related with ipv6.
Several years ago when i setup this server, i was not confortable with ipv6 so i try to disable ipv6 but then was appearing several errors so i enable ipv6 again from network interface but trying to ignore that ipv6 exist until now where i am trying to figure if my issues are ipv6 related.
I have 4 network interfaces but only one is enabled and configured with ipv4 and with ipv6 fe80::6451:b137:ad7f:10de DNS ::1
I look into DNS Manager and only references to ipv4 here, i saw that i remove ipv6 address from DNS queries.
In IIS Manager i can see that i don’t have any bindings regarding ipv6
My router is handling ipv6 from wan but from Lan ipv6 is disabled.
So after reading this it appears to me that something may not be working well this way, my question is what should i do? Try do disable ipv6 a litle better or enabled and configure ipv6. Either way, how can i do this properly?