I think you have to release them to your inbox after you clear out old messages.
i have had the same experience. Inbox folder 100% full new messages are on hold till you delete or file away to make room for the new ones. after i make room in my inbox, i click on "release on hold messages " and then they can be read.
"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson