OK that makes sense, M will be for Mode, ie all of the parameters. Maybe going up and down will let you see a parameter that needs setting but without a list I doubt you wont know what they mean. Maybe if you download a manual for one of their other VFDs the parameters will be similar, I found one yesterday for a MD2005 or something like that. Could possibly be that the external buttons have been disabled because they had a remote pot on it for speed control and a switch for Fwd/Rev. Again without knowing the terminals or the parameters to select it will be difficult, but maybe there is some indication of where a pot would connect, moulded into the terminal block.
Hood