Almost all mags have a specific linear evolution path that leads to having only 2 photon blasts.
It doesn't happen because the third evolution isn't yielding a photon blast, but rather because the photon blast in question is the same as the one you received at the second evolution.
You can view the specifics below. Changing class and section id before evolving to get the photon blast you need is often recommended.
As a sidenote, I'm not sure how many levels you raised on another character, but the evolutions starting at level 50 only trigger every level divisible by 5. In your case, only level 195 and 200 remains for evolution. Also, if you got a special evolution mag already, you're out of luck as they never evolve again regardless of stats/class/section id.
Some of the special evolution mags include:
Deva, Rukmin, Sato, Rati, Pushan, Bhima, Savitri, Dewari, Nidra and of course all of the mags you get using mag cells
By the way, special evolution mags never receive photon blasts upon evolving.
Edit: I just saw you have a sato which means the mag in question will sadly never receive a 3rd photon blast
I've never encountered this myself but hopefully you're able to get it sorted. 3rd photon blast activates at level 50 every time afaik so you should have had them long before it was even able to become a Sato