Describe the bug
I've uploaded the Example code SimpleRTC with clock source set to LSE_CLOCK.
When I compile, there are no errors. But after I upload it, clock seems to be not working.
When code is uploaded with LSI_CLOCK everything is fine.

Expected behavior
As per code, time should be shown in serial Monitor. But nothing happens.

Screenshots

Desktop (please complete the following information):

• OS: Win 7
• Arduino IDE version: latest
• STM32 core version: 1.9.0
• Tools menu settings if not the default: default
• Upload method: Serial.

Board (please complete the following information):

• Name: Bluepill
• Hardware Revision:
• Extra hardware used if any: CP2102 for uploading

Additional context
I need help.