B1/B2 renweal rejection

I had my U.S. visa renewal interview recently, and here’s my profile 20’s Female single Nationality: Jordanian Profession: Medical doctor Employer: Ministry of Health in my home country Purpose of Travel: To attend National Conference & Exhibition, taking place September Visa Type Applied For: B1/B2 visa renewal (I had a previous same type U.S. visa, now expired) Invitation: I had a full registration and an invitation to the conference

exactly what happened:

The officer greeted me:

Officer: Good morning. Me: Good morning. Officer: Can you give me your passport? Me: Sure. I handed her my new passport, along with my old one, which contains my previous U.S. visa. Officer: Thank you for bringing the old passport, but we only need the new one.

She looked at my DS-160 and said:

Officer: So, you’re working for the Ministry of Health? Me: Yes, I am.

Then she asked:

Officer: Where are you going? Me: I’m going to the United States to attend a medical conference in pediatric. Officer: So, you want to be a pediatrician? Me: Yes, in my country.

She asked about my last visit to the U.S.:

Officer: What hospitals did you train at? Me: I mentioned the two hospitals where I trained. I also told her I had confirmation letters from them. Officer: That hospital is huge — that’s impressive. We don’t need the training letters but thank you for bringing them.

Then she asked for my conference invitation:

Officer: Can I see the invitation letter? Me: Sure. I handed her the letter.

Officer: Are you presenting a poster at this conference? Me: No, I’m just attending regular sessions. But in upcoming conferences, I might present a poster.

After that, she began typing on her computer. Then she looked at me and said:

Officer: Doctor, I’m sorry, but I cannot issue you the visa.

She handed me the blue refusal slip. Me: Okay. Thank you.

Can you inform me what I did wrong 😔 how can I improve my chances in getting it