meldas 500 problem

We have leadwell V40 vertical machining center with meldas 500 system , and control unit model meldas FCA50M , when we open the machine that control unit display flashing AL 91 then 80, 00 goes like this then again begin same code AL 91 at the same time monitor has no character like a broken tv, ....etc, we checked battery of this unit but battery voltage is ok, everything is look like ok, just control unit has those alarm and monitor has nothing does any one know what happened or how can we do for the solution?

Thanks & Regards