Wp Ultimate Csv Importer doesnt import

Hi, I was using csv import without any problem. But suddenly it stopped to work. I dont know why, maybe after upgrading or else. The problem is When i try to upload a file nothing happens. The loading never even start. I checked my error.log file up but i didnt see any error for csv importer. It was working great it happened suddenly maybe after updating. I downgrade it but didnt work and also disabled all my plugins and tried again but no solution ?? What can cause this problem ?