customized opencart extension stopped working

A customized opencart extension for bulk products upload suddenly stopped working. I have no contact with developer at the moment so need someone else to check the issue. You can see the attached screenshot. When I click on select files and add any pictures, the files are normally uploaded one by one and for each picture a separate box appears below converting it into product with description and details mentioned above, but now it is not being uploaded without any errors and nothing happens. The screen remains the same. Also the "Add Product" button is not working. I was daily using this extension without any issue but it suddenly stopped working whereas i had not done any changes or updates nor added nor removed any extensions, etc. I changed php version also but that too did not helped.