I created my form in the new responsive designer, the attachments field I customized it to accept "docx,xlsx,pptx,pdf,jpg,jpeg,png,msg,gif,html,htm,zip,rar,rtf,csv,txt,doc,xls,ppt" , attaching files is working fine, but after people attach files to their list items, though we all can see there are files attached, there's no way to open them, if I double click on them, nothing happens
I had this previously, it was when I had a workflow updating the item, which in cases of large files or slow connection meant there was a change conflict between the file uploading and the workflow updating something on the item. This mostly happens when there are multiple attachments as unlike the old responsive designer, the new one doesnt upload all attachments at the same time, it loops through them adding 1 by 1 (you can see this in version history).
You can see the conflict error if you use the developer tools and recreate the users upload action.
I raised a support ticket and the best solution was putting a pause action on any workflows updating an item on creation, although that seems a crazy permanent solution to me, especially as you have to guess how long files will potentially take to upload in order to set the delay.