Why did we receive Box2 at room temperature when the label indicates it has to be stored at +2°/+8°C ? Is the solution still usable?

Yes, the Box2 is still usable. The Box2 has to be stocked between +2°C and +8°C but it can travel at room temperature for 5 days. In that case the reagents will not undergo any mutation nor damage. It is just important that the Box2 be stored between +2° and +8°C as soon as possible after reception.