I have seen this a few times with Local Folders. Restarting eM Client always seemed to resolve it.
I have closed and restarted sevearl times today; any ideas since I still have same problem as yesterday?
One thing you could try is to close eM Client and run C:\Program Files (x86)\eM Client\ DbRepair.exe in case there is some problem with the database.
Is this with Local Folders, or folders on an IMAP/Exchange account?
My recent Folders Created for TracFone and (Brothers) are O. K. and all seem to be fine Again; I did try prior idea and it showed nothing bad or good!