XBOX Can't Slot Skill Gems in Meta Gem

I feel really dumb, but I'm trying to slot the Sniper's Mark skill gem into the Cast on Elemental Effect meta Gem, but I'm having interface troubles.

I can slot the Meta Gem into the skills tab and it shows with its 4 slots (and I can devote Spirit to the meta skill). But when I select the Skill gem, the curser skips right over the support slots like they're not even there (this happens whether I pick the gem up with the A button or use the X button to "Slot").

The only things I can think of:

1. I'm using the buttons wrong and there's a different way I need to be setting this up.
2. The skill gem I'm trying to use is not eligible to be slotted there (I'd like to know what I'm missing if that's the case).
3. I guess it's possible meta gems are bugged and it just won't ever work.

Any help anyone can provide would be much appreciated.

My understanding is that you need to socket a skill specifically with the "Spell" tag into that meta-gem. Sniper's Mark does not have a spell tag, its a "Mark" "Duration" skill.

That sounds right. I'll search around tonight for a Spell gem and see if that fixes the problem.

Cheers, and thanks for the help!