laptop Not powering up

Probably not dead, and please stop holding the power button.

Esc, F1 and F4 lighting up in sequence is a ThinkPad telling you it is doing memory retraining: it re-initialises the RAM and runs a test on it, with a blank screen the whole time. Lenovo's own hardware maintenance manual for this model generation says it plainly: "When memory retraining occurs, the screen might be blank. You might see the LED indicators on Esc, F1, and F4 blinking sequentially to indicate the progress. Do not press the power button to interrupt the process. Wait a few minutes until the logo screen is displayed."

They dropped the POST beeper on these machines, so those three LEDs are doing the job the beeps used to do. It reads as a fault and is usually the machine working.

What turns it into a real fault is interrupting it. Every press of the power button starts the retrain again from zero, so a laptop that keeps getting cut off can blink for hours and look bricked.

The test, one pass only: plug the AC adapter in (a retrain can stall on a low battery), press power once, then touch nothing at all. No keys, no lid, no power button. Watch for up to 15 minutes for the blinking to stop and the Lenovo logo to appear.

Tell me one thing either way: did the blinking stop on its own, and had you pressed or held the power button before that? If it runs past 20 minutes with no logo, that is a memory module failing to train rather than a retrain finishing, and the next step is the bottom cover off and one RAM stick at a time.

For where to check me: the wording above is from Lenovo's Hardware Maintenance Manual for the T14s Gen 5 (download.lenovo.com, the memory retraining page), same text as the T14 Gen 4 manual.