only some push subfolders syncing

I have numerous subfolders from my Outlook Pushed to my Mail app. But once I close out of the Mail App and reopen, 3 of the subfolders are no longer linked. They are a lighter shade of grey in my Mail screen and will not let me quickly access those folders. I have to go into my Exchange account and scroll down to these subfolders to access the mail inside. Has anyone had a similar issue, and do you know how I may be able to get these folders consistently synced with Mail?