Try another browser. Or another browser mode (mobile, classic, or desktop).
Or try using the eBay app to read your messages.
If you have your messages sent to your email, try reading your messages in your email.
If you are using a desktop browser, try switching between the new chat-style format and the older classic format.
Try using an alternative link to read message from members, such as this one:
https://mesg.ebay.com/mesgweb/ViewMessages/0/m2m
