I think you have made a great form plug in, and I have been testing it in a localhost MAMP environment. I set up one form with various fields including some image uploads, and then tested it; this would have been about a month or so ago. Everything seemed to work. I knew that when the site was going to go live (not yet) that I would be creating more similar forms (I began creating another one), but as the test worked I left it.
Now I am closer to live date, I tested again to make sure nothing had changed but now if i try to upload images I get an error message (front end). When i went to look at form settings and fields, the file upload fields i had put in my form were still there, but the option to add more was gone; I tried to create a new form and it was missing from there as well.
This morning I saw there was an update so i have applied that but still no change. I have tried looking for jQuery conflicts as suggested on the plugin site but there are none that I can see; I have tried deactivating all the other plugins but nothing changes. Can anyone suggest a fix for this, or is this feature now only available in the Pro version? I can't find any documentation relating to this issue anywhere. I am going to try deactivating Ninja Forms Lite, deleting it and then reinstalling to see if that makes a difference as well but given that the update didn't change anything I'm not optimistic. I would appreciate any help at all on this.