Hi Maarten thanks for your answer!
Like you said the ACCL is a pesky one. As I recall like two/three years ago our Account Manager (not from Check Point, of the partner) told me the old ADN (Advanced Networking) changed to ADNC (Advanced Networking and Clustering). In the moment I didn't give major importance of this, but I believe now when I upgraded the gateway I lost this feature. Nevertheless, I didn't find documentation regarding from which blade/license is SecureXL tied to.
For now I tried to reissue the license from the UC, installed it and update the contracts from SmartUpdate. Installed then the database and finally installed policy on the conflicting gateway, but the situation remains. I've a pending reboot of the gateway as a last instance, but I don't think it will be any difference.
In the meanwhile I asked the partner to open a case to TAC, as for my support contract doesn't allow me to do it directly.
Also, if it's useful, in the conflicting gateway object, where it says SecureXL it has a blue "i" letter and a window pop ups telling "This feature is controlled from the gateway".
And also-also, in the UC the ACCL blade-related license appears like this: "CPSB-ADN - Advanced Networking and Clustering Blade now replaces Advanced Networking and Acceleration and Clustering Blades".