@lkoenig
You were correct about the rule being applied to all. I created a new folder for hosts and changed the condition to apply to the newly created folder.
As for permissions I am at a loss. For testing I added the admin credentials of vSphere to CheckMK and it still fails with the same error.
@martin.schwarz
Firewall rules are in place. But I will take this and contact out network guy to see if there’s anything that might be causing this issue.