While plugged in and charging, it should show a charge activity indicator on the right side (three horizontal bars flashing from one, to two, to three), indicating that the device is being charged. Once charged, it will show an outline of a battery symbol on the left. The device should connect to a compatible phone/tablet even while being charged, so please try connecting to the app while the glucometer is charging to rule out any connection issues.
After the device is fully charged (look for the outline of a battery symbol while plugged in), pressing the "M" button on the opposite side from the USB port should result in all the lights being on for a brief second and three horizontal bars remaining on screen for a few seconds. If the app that has connected with the Glucometer is open and the Gluco+ device with the correct serial number is selected, the glucometer should be connected (according to the app) and display the Bluetooth symbol.
Please let me know what your device looks like while charging and when fully charged, as well as when the M button is pressed and the app is connecting with the unit.