The Wifi connection between the mobile device and e-mark is weak - try to operate the App directly next to the e-mark. If the e-mark is directly beneath your mobile device, check whether your smartphone or tablet is really connected to your e-mark.
In case you are surrounded by many Wifi networks, the time to transfer imprints can increase significantly. You can try to switch your e-mark to another Wifi channel to overcome the crowded Wifi networks. For that, go to the settings in the App and select your e-mark under 'My e-marks'. When you are connected, you can change to another Wifi channel - between 1 and 11. On default the e-mark is operating on Wifi channel 6.