Hello Giannis,
The cutoff database, and the en15804 database are not the same. You cannot use the EN15804 LCIA method with cutoff processes. If you have the EN15804 add-on, you need to download the EN15804 U and EN15804 LCI database from nexus, and use these processes instead. This will give you results on the categories specific to EN15804.
Best of luck.