Sorry if this is blunt.
The bun definitely looks unprofessional and messy for the type of office that you work in. It just looks like you rolled out of bed and didn't really brush it. I know this was end of the day, but in the corporate world there's no excuse for your hair to look like that at the end of the day. I think your boss was looking out for your best interested by letting you know what's up. You may need to take a day or a night after work and play with different hairstyles in order to figure out how to try something different. I took me some time before I mastered different styles, but practice makes perfect! I wish you the best.
**My hair is in the 3cish range and what helps laying my hair down is braiding my hair into tight plaits after I wash and letting it air dry. This week after I let my hair air dry and unraveled the plaits, I combed my hair with a wide tooth comb and then I put a healthy glop of conditioner on my hair and brushed, made a bun and put a scarf over my head. I havent brushed my hair since this morning, so I hope it works
View attachment 56958 ***