Please see the picture below:
Please help. Stuck on 3/4 of Brilliant event.
Some Potions, like Exstimulo, are Encounter-only. To use them, you need to be inside the Encounter, then tap the Potions button at the bottom right corner of the Encounter screen.
@BabaYugga You can only use them if you've already engaged a foe. If so hit the bottle in the bottomright corner and you can choose exstimulo potions as well.
It is fixed now, but it was not working when I was engaged with a foe either.
The Potions button is displayed during your offensive attack in this case.