We can't be sure where the bug is here so talk to email host support about how to track it down. I've found support to be lacking for Windows Live Mail so good luck with that. I'd change to another email client if possible. In short, my experience with WLM was that bad.
I have Windows Live Mail on my desktop PC. Mail is set to leave a copy on the server for 5 days. I have Windows live mail on a Windows 7 laptop and a Windows 8.1 tablet. Both the laptop and tablet are set to leave a copy on the server.
My wife reads her mail on the tablet in the morning then closes the program and turns the tablet off. When she goes to her desktop and opens Win Live mail the mail she just read on the tablet does not show up. She can go to a webmail program and the emails show up there. Also when we travel the laptop is doing the same thing.
My question is why do the emails not show up on the desktops after viewing on the laptop and tablet with both set to save emails on the server?