FlashForge Invertor I resume not working

I normally print models on the Flashforge Invertor I from the SD card and somehow I cannot get the resume feature to work after a power outage.

The LCD screen shows thet Resume off which means it is On as per the user manual. After a power outage a screen pops up that asks whether I should resume printing and when I press resume it just goes back to the default screen and nothing happens.

When I asks the local dealer from where I bought the machine he said that "Resume" only works when the models are transferred to the printer via wifi.
I hope someone can help me out here.

Many thanks!