Hello,
The breakthrough power system is not based on books or vials. It is based on the number, amount, and rarity of breakthroughs you possess for that unit, with each level of breakthrough giving a number of points that move you toward the milestones of power accrual. Most likely the breakthrough you reached simply didn't give enough points. If you'd like to learn more about this system, please check out one of the guides in the strategy section of the forums or on the official discord.
Thanks and have a great day!