To check if there are any filters currently active:
In the top left of the Inbox, click Change Filters.
There should be two columns of options which are Days Since and Read/Unread. By default, they will be set on Last 7 Days and Unread Messages Only.
Change Days Since to All and Read/Unread to All Messages.
In the top right, click Refresh. This will pull through all the new emails that now fit the new criteria.
