It is a mess, with auto FMS audate.
I had to uninstall SimPrief and after this to delete, and the x-Plane 12 folder, and re-install X-Plane 12
Then I do not remember from where (I hope to find again for the next AIRAC), I downloaded the AIRAC 2304 manually, and place it in custom data.
It is now Ok and with Zibo 737-800x
SimBrief should make easily accessible a manual Update.
(from a remote Island in Northern Aegean Greece)