Messages can be glitchy from time to time, are you still having this issue, as I see you posted this question yesterday, so sorry for the late reply!
If you're using the app, there have been more than the average tech issue there, so if you can, switch to a laptop / PC and try Chrome, that seems to work well with eBay. Clearing cache and cookies may help too, and try from there.
@whitejordan2008
