Twitch Prime connect issue to EA (PS4) - "Something went wrong" Invalid Request

Hello Community,

this is the last hope I have to find a solution for the connection issue between the Twitch Account and EA Account.

Intro: After I paid for the Amazon Prime, I went to the Prime Gaming Website to claim my Prime Loot for Apex Legends (Horizon Skin).

After I did this, Prime Gaming asked me to connect my Twitch Account with my EA Account. After some more steps and logging into Twitch AND my EA Account, I keep getting following Issue from EA: "Something went wrong - Please close the application and try signing in again." - see picture below

Twitch still says: "Connected to Electronic Arts" - but on my EA Account there are no connections listed

I already tried following solutions:

1. Unconnect EA from my Twitch and retry the whole connection process

2. Trying out 5 different browsers (Chrome, Edge, Firefox, Opera, Safari)

3. Trying out 3 different devices (Laptop, PS4 and my Mobile Phone iPhone)

4. Contacting Prime - No solution given 

5. Clearing Cache from every browser

6. Unconnect with this EA Tool on the EA Website

So after every try to connect Twitch with EA it keeps giving me that invalid request info "Something went wrong" - but after some seconds the connections appears on Twitch, but not on EA, neither I receive my Prime Loot ingame.

I am really frustrated and I have no idea anymore. And I am tired of being sent from one support to the other.

I really ask for your help!
Thanks in advance.

Dean