I'm very sorry to hear that you didn't unlock a portrait in SWGOH after completing a training mission. I completely understand why that would be frustrating. I'm gonna provide as much information as I can.
I sadly must inform you that we're not able to add portraits manually to player's accounts so there's not much we can do in this situation, I'm afraid. I do apologize for any inconveniences caused.
I'll mark our case as a potential bug for our game team to review further. Note that you'll generally not receive a direct response from them, but should an issue be identified they will look to address this. Compensation may then be provided at their discretion to those affected.

I'm sorry that there wasn't more that I could do for you here today but if you have any further questions or if there's anything on your mind,
you know you're more than welcome to contact us again.