USB-C charging on Envy X360 Thunderbolt port

[Victor_G55]

There is another post from a couple of years ago asking a similar question but the answers are not relevant so hopefully here can get the help needed.

I have the Australian version of the Envy X360 model 15-CP0012AU.  There is a USB-C port which has the Thunderbolt symbol but the official spec does not mention Thunderbolt, only that it is USB 3.1 Type-C Gen 2 and apparently with power delivery.

I tried connecting a Cygnett 20amp power bank with a standard type-A  to type-C cable with the computer off and the orange charging light comes on but when I turn on the computer a message says it's not charging and suggests connecting the charging adaptor.  At the time the internal battery had 88% charge.

Can this model be charged through the USB-C port with either a powerbank or from a wall charger?

Another oddity is the type-A port also has the Thunderbolt symbol and 'SS' marking but my understanding is that Thunderbolt only applies to type-C connection.  What is the explanation for the Thunderbolt symbol on both ports?

All advice appreciated.

[Huffer]

It's not a Thunderbolt icon. Looks like it but is really HP Sleep and Charge. 

See p. 4:

Service Manual 

Your usb-C port is not "Power Delivery" so will not charge the laptop, probably. If it could it generally will only accept a charge from a device with at least 35w of power. Some exceptions to that. For HP laptops if it can charge by USB-C that is the adapter HP ships with it and if, not you get a barrel type adapter. 

[Victor_G55]

Firstly thank you for the comprehensive reply.

There is still some confusion though because the official HP website states in specifications "USB 3.1 Type-C™ Gen 2 (Data Transfer up to 5 Gb/s, Power Delivery, DisplayPort™ 1.4, HP Sleep and Charge)" linked here https://support.hp.com/au-en/document/c06044226 .

Your thoughts again much appreciated.

Victor