The most common reasons of an empty board or visible items are fewer than earlier are:

• Filter is applied on the board, check if there is no filter applied on the board by clicking on Reset Filter button.
• Check if correct Project is selected
• If contents are deleted mistakenly by any user, you can restore User Stories and Issues from Yodiz
• Recycle Bin (which can be found by clicking on the icon at top left corner of the navigation menu).

Note: Recycle bin access is administered by Super Admin, check your access rights.