I have an HP Envy x360 (15t-cn100). According to the specifications, my laptop should support USB-C 3.1 Power Delivery. It is my understanding that my laptop should be charging when connected via USB-C, however it is not.
You’ll notice that it does not explicitly state that the port accepts power to charge the computer (HP is good about including that in their use manuals). It is a bit misleading because while it states “with HP Sleep and Charge”, it actually is referring to the ability of the port to provide power to other devices while the system is off.
It looks like HP may have made a mistake on that product page by including the term Power Delivery. This is further evidenced by the fact that you were able to rule out the dock’s hardware since it charges another system. If I’ve misunderstood something, please let me know.