Error while trying to get my Access Token

Hello,
I have purchased the Aliexpress plugin and it seems to have been setup correctly but when I try to activate certain features like Product Sync or fulfill it says I need to get an access token.
When I click on the button I get the “Update” screen where my Key is and at the bottom there is a section for Aliexpress API with the option to get access token. When I click this it opens a small window for me to authorize which I do then it loads for a moment and give me an error “Data invalid”
I am already logged into my Aliexpress account and I have also tried it multiple times yesterday and today and on different browsers (Iexplorer & Chrome) and on 2 different computers.

Please help me

Thanks,
Rainer