I have tried all the solutions given on the internet but the "Upload multiple files" option comes one time and then it becomes disappeared.I fell something is stopping the option to show and perhaps it is Symantec antivirus which stops to show the option.Then after some attempts it was working.The steps which I have done are:
- I uninstalled the antivirus.
- Checked that STSUPLOAD.DLL is present in C:\Program Files (x86)\Microsoft Office\Office14 folder.(If does not exists then download and place there)
- Go to browser and checked Tools--> Manage add-ons-->STSupld.UploadCtl is enabled or not.(If disabled then enable that)
- Delete browser history and close.
- Reopen the browser and check the option is enabled or not
