ThinkPad E14 Gen 2 No Post with Memory Training Loop
ThinkPad E14 Gen 2 No Post with Memory Training Loop
Did you attempt to start it without the USB-C adapter connected? Your L390 (an older model) experienced issues after a BIOS update—lights would turn on and then go black unless powered from battery. Lenovo eventually fixed it, about six months later, thanks to an allowed BIOS downgrade so you didn’t have to constantly plug and unplug.
The USB-C adapter refers to the power supply unit. The internal USB-C port is permanently attached, suggesting it's the PSU you're thinking of. I've also attempted this, but it still encounters the same problem when using the internal battery. I'll check if my coworker made any updates around the time he relocated his gear; if so, it could indicate a BIOS-related issue.
Reset the laptop using a pin or paper clip. Place a small hole for 5-10 seconds. It was located at the bottom. Reconnect the power supply, then try to power it up again. You might be taken to the BIOS settings to adjust time and date. This method worked for me today.