Thanks Guys for your assistance in this matter!!! Finally incoming calls are working fine!!!
I had to reinstall the FusionPBX starting from 0 and when the Extension, gateway, Destination, Inbound and ACL configured, I still had the incoming call rejected.
Then the only change I did which made the calls pass thru was to remove the domain value on the Node configured with my provider CIDR IP/32.
Remember I was trying to set everything in a different Multitenant domain and I always was trying to limit the CIDR to that domain which apparently is wrong. The CIDR of the Gateway connected provider seems to need full access in every domain or it will be blocked.