Self-stick tiles on painted floor?

I have a roughed-in bathroom on the second floor of my barn. I'm hoping to add some self-stick resilient tile.

The current floor is plywood, but it's been painted (not sure with what - a gray colored, not-very-glossy coating of some sort. Paint? Primer? I simply don't know.)

How do I make sure the tiles will stick to this? Would applying a coat of sealing primer work?

Thanks
Eric