The battery on the Target Board may not have enough charge to start the STM8 for standalone operation.
When you receive your STM8L target board, you should let it charge on your primer base for 15 hours. Note that it takes about 30 hours to fully charge the battery. For charging: follow the instructions here...
To verify the battery charge and VCC on the target board, follow the instructions here...
IMPORTANT. If the battery ever fully discharges, it is IMPOSSIBLE to recharge it.
Power supplies that you can use to recharge the target board battery:
1. EvoPrimer of Open4 base
2. Provided solar cells
3. eventually a 3V external power supply plugged into the jack may be used
Finally, When you are not using the board, make sure that follow the storage recommendations here...