I have tried different L2j server packs and they have the same summon buff display bug where you can only see one buff but you cannot see the other when you get buff such as Blessing of the Queen and Gift of the Queen. I have even played in some server that have the same problem. I google a possible solution, but came out negative. So, perhaps most people do not know how to fix it or this is just a stupid post :P Anyways, here it is a small little guide.
1. go to gameserver folder > data > stats > skills
2. open the xml document where the skill is located and open with notepad, modify the skill where it says:
<effect count="1" name="Buff" time="#time" val="0" stackOrder="1" stackType="QueenBuff1">
3. add 1 as showed above on stacktype on one of the skills
4. Save it and now you can see both buffs display on the buffs bar.
do the same for summon buff Seraphim :D The serverpack I'm using, skills are located on xml 4600-4699 and 4700-4799
Best of luck!
Credits: merino2000