Lenovo Thinkpad T540 suddenly not charging and power button flashing

Unfortunately, out of the blue my Lenovo Thinkpad T450 stopped charging. When I plug in the AC, it simply gives me back flashing lights on the power button (non stop and medium speed). I have tried everything I’ve seen online, from turning it off, removing battery, pressing the power button for 30 sec and then put battery back and plug it to unplugging my CMOS battery and external battery at the same time repeating the procedure. Lenovo avantage tells me my batteries are healthy (or at least before my laptop turned off). It has been off since and I cannot turn it back on due to critical error 0190 Critical Low Battery.

Please help me as I use this laptop for work and uni, got so many files I need to have.

could it be the charger or is it the battery or anything else hardware/software?

thank you in advance!