Wii Balance Board not syncing?

[PencilLeads]

Hey there, bought a second-hand balance board. Have tried swapping out batteries and turning console off/on again, but I still can only get the power light (on the board) to flash when I press the power button. When I press the sync button on the balance board, no light flashes and it won't sync to the console.

Anyone know what's wrong/have any advice? Thx