@justforfun.2010
Try signing in with an incognito browser window in Chrome (or use another browser). If that allows you to send replies to messages, go back to your regular Chrome browser and try clearing your browsing data -- particularly "cached images and files", using the time range "All time", and possibly deleting your individual eBay cookies.
A conflict between eBay's site data and your local cached data can cause many problems, which is why some folks suggest trying another browser as a test to see if the problem is browser related. Particularly when other users are not experiencing the same issue that you are.
