You can contact support. Have you tried getting a friend to use it to summon the Sea Lord and then fight it? Also are you sure you are at the correct stand?
First, I'm going to ask if you're standing next to the correct crystal. (I know, I know.... But when trouble-shooting we always suggest the simplest fixes, first. So just make sure that you're in the right place. )
Next, have you tried logging out, then logging back in and going up to the crystal? Sometimes the game glitches and we can't activate a sigil, but logging out briefly seems to help reset something. Since it's been a couple of days, go on back and give it another try.
While you're there, try walking around the crystal stand until your 'X' option pops up. Try switching realms. If you still can't activate the crystal, you may need to send a ticket to support. They'll get you back on track.
Thanks for the advice; every day I've been testing the crystal stand. Yesterday it randomly let me place the crystal and I got to fight the sea lord. Thanks!
)
Alia Misthaven