Hi

Even if your caste certificate is invalid it can't be the reason for this. Are you sure you uploaded according to the guidelines they gave i.e scanned copy in PDF with the specified file size. If everything is right then try login in again and upload the file. The last date is extended to 1st October so relax and try patiently and they will display list of defective applications on 26th october with a timeline to rectify it. It will have applications which had uploading issues and errors like yours .moreover they have given an additional date for change of category so you have more time and opportunity and check the validity of your certificate if its invalid renew it you have time till 12th November. Don't do mistakes as there will be no more chances further. Get back to us if you have any other query.