Hi @h4bu
Try a full power refresh first to see if that resolves the problem.
Disconnect the charger if connected and then remove the battery from the laptop.
Since you already have the laptop open, disconnect (unplug) the coin cell battery (seen just below the fan in the image you posted) from the motherboard.
When the coin cell battery is removed, measure its voltage. if it is <2.4V DC or is older >4-5 years, replace it. Search online for [https://www.google.com/search?client=firefox-b-d&q=zx50vw+cmos+battery|ZX50VW cmos battery] to find suppliers that suit you best. (examples only)
''Then press and hold the laptop's Power button for a full 30 seconds and then release it.''
Reconnect the coin cell battery, reassemble the laptop, reinsert the main battery, connect the charger and check if it turns on OK.