The number of file uploads at once is also control by php settings as well as the max upload size. Make sure the php.ini settings are correct. Then in the server settings look at the header size there as well.
Not the header size, check the settings for max body size; not sure about Apache, in Nginx this will be in the server block for the website.
Fixed! It took increasing the total upload size
Glad that I could be of some help. Sometimes it is the simple things.
