Led blink once and LCD with a row of squares : help me

Hallo.
I finished to solder 56input kit.
When I power up it,
I see tha the LED blink only once and in the LCD I have a row of squares without text.
What could I check?
Thanks.
Mario
I finished to solder 56input kit.
When I power up it,
I see tha the LED blink only once and in the LCD I have a row of squares without text.
What could I check?
Thanks.
Mario