Hello, @st7878,
Actually, the option you used to change the cart icon in the header is used for the Desktop and Mobile header too, https://postimg.cc/HVs0rV86
And the option you are trying to change under “Mobile Panel”, is used for the sticky mobile menu section and it has the 2 possible icons for the cart: https://postimg.cc/vccgR9Vw other than that you can add your own icon as well.
But if you want the same icons as for the headers then you can upload them by yourself, you can download the icons from Google as per your requirements.
Regards 8Themes Team.