Hi Jscallan,
Thanks for reaching out to Apple Support Communities. It sounds like you're having an issue with sending Live Photos via iMessage. We're happy to help.
When navigating to Settings > Messages, is the option for "Low Quality Image Mode" turned on? If so, does the issue remain with the feature off?
If the issue continues, make sure the settings and steps in article here are completed: Take and edit Live Photos Specifically, the section "How to share your Live Photos." You can also find out more about the requirements for the feature in the "Learn more" section at the bottom of the article.
Should the issues remain after checking the settings, complete a normal restart of your iPhone and test:
Restart your iPhone
Best!