Please Ignore this issue - admin error! I worked out that the problem was due to the user profile images were missing from the server (we deleted accounts over summer but realised we had got the wrong ones and restored the database but not the profile images). We restored the images and uploads are working as they should.
General help
File Picker not working M3.3.2+
ការពិភាក្សាត្រូវបានបិទ ដូច្នេះអ្នកមិនអាចឆ្លើយតបទៀតទេ។