Just fixed it and the display is working correctly.
It may be 'working' correctly but you are not using it correctly in your present sketch.
The display does not need to be refreshed. Anything that you send to the display stays there until it is overwritten or until the power is removed.
The message "hello, world!" doesn't change and therefore, in the original sketch, it was sent to the display once, in setup().
The 'number of seconds since reset', in the original sketch, changes periodically and therefore is rewritten to the display each time around loop().
Don