Your settings for MMS (Multimedia Messages) may be turned off.
On you device go to Settings | Messages | then scroll down and under SMS/MMS
make sure you MMS option is turned on
Another issue may be how your device is connected to the internet; Cellular or WiFi. Some Cellular networks using APN will not allow images being sent or received by default. However you may be able to edit this.
Apple provides a support article that explains the above:
If you are not using an iPhone but rather a Windows 10 Phone (Lumia for example) then read this Microsoft Article instead that explains the same thing:
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.