Some Matrix users are experiencing an issue where they are unable to upload documents to their listings. This has been traced to a known issue with Safari versions 14.0.1 and 14.0.2 that is preventing popup windows/upload boxes from opening. This issue is not specific to our Matrix system- users are experiencing it on many sites (Dropbox, email clients, etc.).
Apple is currently working on Safari version 14.0.3, which is expected to be released in the very near future (January 2021).
Until the new version of Safari is out, it is recommended that Mac users access Matrix from Chrome or Firefox.