Have the same issue on xiaomi mi 11, every time I must delete app data via application manager andonly then am i allowed to open the app once. Then the same all over again..

Same. Just reinstall it it will work fine. Its just that your downloads list will get deleted along with it. In order to get it stated again. I recommend that you go to files and move all the movies you downloaded from popcorn files and place them anywhere inside your phone. The reinstall the apk. The movies you already downloaded won't show on the downloads list in the app after reinstalling it.