So for some reason in a battle im doing the ai just isnt terastilizing.... its a double battle. they both have 1 pokemon each and a tera orb. im not sure if them only having one pokemon is the issue.
Edit (5/19)
Found the original issue, didn't have tera on however its still not working properly as in a 2 person double battle its only terastilizing once and its when theres only one pokemon on their side rather than for each trainer.
It works just fine for me. The AI is either simply unable to Terastallize, or has determined that it isn't advantageous enough to waste Terastallization (based on its skill level).
For example, I tried a double battle with opposing trainers with the following Pokemon on the field:
Rattata [Tera Normal]
Spearow [Tera Normal]
Vs. the player's Pikachu and Pidgeotto.
The AI Terastallized both Pokemon, since it's advantageous for both Pokemon to do so due to having Normal-type moves to utilize.
I ran the same test with the only difference being Rattata being given Tera Ghost, and the AI chose to only Terastallize Spearow, since there was no offensive advantage to Terastallizing Rattata (since it has no Ghost-type moves). The trainers I was battling against were low-skilled trainers (a Youngster and a Camper), so
only offense is taken into consideration with Terastallization AI.
Against higher skilled trainers, they may have determined Tera Ghost was actually useful for Rattata despite lacking any Ghost moves, since this would have given Rattata defensive utility against Pikachu and Pidgeotto's Normal-type moves.
EDIT: If you wanna test this yourself, just turn on battle logs in debug mode to see the exact scores the AI is calculating to determine if it should Terastallize.