Ive tried with many different files, same result. Also tried reconnecting the account. Licences are valid. All other features work fine.
Online version of Adobe Acrobat shows blank "Organise Pages"
Hope you are doing well and sorry to hear that.
As described, the online version of Adobe Acrobat shows blank "Organise Pages", would you mind sharing the link you are using? Please try with the link https://acrobat.adobe.com/link/acrobat/reorder-pages?x_api_client_id=adobe_com&x_api_client_location... and see if that works.
I tried to reproduce the issue on my end and its working fine. Please try to clear the cache of the browser and check. You may also try using a different web browser.