How come Cobalion and Virizion won't spawn in Omega Ruby?

I have completed the game and I have 4 legendaries to catch.

These were Cresselia and the 3 deer trio, which are Terrakion, Cobalion, and Virizion.

I have 3 Pokemon with max EV and I caught Terrakion on a Tuesday. A day later when I went back to the portal to them, which was when Cobalion was meant to be there, nothing happened.

I waited a day later and still, nothing happened. It just keeps saying that "a mysterious ring is floating in the air."

Please help, because I really want to catch Cobalion and Virizion and it isn't working!

Solution 1:

As per my answer here: What are the prerequisites to encounter the legendaries in ORAS?

Terrakion/Virizion/Cobalion

• Available on: Both Omega Ruby and Alpha Sapphire
• Location: Pathless Plain (Eon-Flute, Red Spark Near Pacifidlog Town)
• Required Party Pokemon: 3 Pokémon fully EV-Trained (Obtained once a Pokémon's stats cannot be raised anymore.)
• Required Item: None
• Date/Time available:
  • Terrakion - Tuesday/Saturday
  • Virizion - Monday/Thursday
  • Cobalion - Sunday, Wednesday and Friday

If you've met all the prerequisites, then you should first confirm the date/time on your 3DS. Ensure that it is set to the correct day for them to spawn. If you change the date/time on the 3DS, all time based events (including legendary spawns) will be disabled for 24-48 hours.

If your 3DS is correct and there have been no time/day based changes in the past 24-48 hours, then the only other cause for them not appearing is that you've previously fought them. You will need to re-defeat the Elite Four in order to have them spawn again.