I have a Lenovo Thinkpad that won't charge with the charger (yellow rectangle tip). It will charge when connected to the Lenovo docking station, which utilizes the yellow rectangle tip and usb-c port simultaneously.

I don't have the option to utilize simultaneous usb-c tip and yellow rectangle tipped charger cord when not on the docking station. I feel like an idiot that I can't figure this out. Any ideas?

I suspect the charger or the charging port might be failing.

You can Amazon a charger and if that does not work then next step is the port.