After taking the effort to actually find the entrance to Oluwa Cave you will come across a drawing on the ground that will be the main quest objective. When you hover over it you will see a prompt to interact with the objective but when you attempt to do this, nothing happens. The icon will go full circle but it will not complete the quest for you.
This is a bug with the game. Even if you have all of the relics, you will not be able to interact with the quest objective. Thankfully, the solution is pretty simple.
Fix The Glitched Objective In Triadas Blessing
The video guide below shows the time when I had the exact bug. If you are observing the exact same issue, then watch on and you will find the solution.
To fix the glitch, you simply need to reload your last autosave from the settings menu. This will bring you back to the same room you are already in. When you try to interact with the objective this time, you will be able to actually do it and be able to progress on with the quest.