It narrows down to an unavailable firmware update on the camera side from Nelly's security.
I bought it from them from a user from this forum who suggested me this specific one.
Waiting response from Nelly's stuck with an incompatible camera with BI.
I attentively re-read & re-applied absolutely all of the advices since the beginning of this thread.
I got to the point of shutting down windows defender, after shuting it down with the whole windows firewall with no results. Re-started PC, manually added
Blue Iris admin software and services inside windows firewall... nothing. Restarted and put everything back like before.