"Open dispute" link not operational on android app

I did not recieve some of my ordered products and the "open dispute" link is not working on the android app for me to claim my money back from the supplier. I have tried in vain to contact Aliexpress about this. I have updated the app but it still says "under construction" when I click on "open dispute". I struggled a lot to get hold of an online chat agent and when I finally did, the person could not help me. I was a big supporter of Aliexpress but if it is so difficult to lay a complaint about a system error on their part, then it becomes too big of a risk for me to keep supporting them.