Often this is completely normal. Your device is designed to switch off in two situations, so it is worth checking these first.
If neither of these explains it, run through the full setup below.
Place the discs and remote in the case and charge them for 2 hours. Charging is complete when all four lights on the case are solid green.
Take the discs and remote out of the case, then press one gel pad firmly onto each disc. Leave everything switched off for now.
Press and hold the M button on each disc until it beeps. Only switch them on, do not press + or − to change the mode.
Press and hold the M button on the remote until the display lights up.
As you adjust it, both discs blink in sync. This confirms they are connected and working together.
Place the discs on your back and begin your session.
Enjoy your full 15-minute session.