you didn't state what specific model monitor you have, but if it's like the EBY-701; the tabs (that you may be referring to as "levers") are basically little handles for a plastic 'wedge' that slides under the ribbon cable to secure it.
the connector's electrical contacts are on the top (facing down, towards the board). the ribbon cable's electrical contacts are on the white side. obviously the connector's contacts need to touch the cable's connectors (the blue side should face down, towards the board). when the 'wedge' is pushed into the connector, it pushes the ribbon cable up against the top of the connector (this makes a solid electrical connection and secures the ribbon cable).
to re-insert the cable; make sure the 'wedge' is pulled out (it should only slide out about 1/8"), then insert the cable into the connector and slide the 'wedge' back in.
--the electrical contacts will not make a good connection unless the ribbon cable is pressed up against the top (inside) of the connector. if the wedge simply broke free of the connector, then you should be able to push it back in. if the 'wedge' broke into multiple pieces then you can try to manually push the pieces under the cable, or use something else to wedge the cable.
good luck