Can’t send pictures or videos to non iPhone users

A photo or video message to a non-iPhone user is called an MMS. These messages are normally chargeable at an extra fee from your carrier.

Do you have a safety buffer? Some networks have this in place to avoid going over your allowance, one reason you might be unable to send a photo/video to a non-Apple user via MMS could be that you have already reached this buffer.

You might also want to take a look at the following resource for help

If you can't send or receive messages on your iPhone, iPad or iPod touch – Apple Support (UK)

MMS is a carrier provided feature, so you'll need to contact your carrier for help with this.