Hi. New here. I have just bought a factory refurbished Zumo 346LMT-S. It's great but I can't seem to get it to update the maps. I get a message saying 'not enough memory' though I have put an 32G SD card in. The file size is 8.4G which seems quite big for an 'update'. I don't have a laptop, just an android tablet but the manual says I can do it over the WiFi directly. But it won't. What am I doing wrong ?