Map pin icon doesn't work

I have a problem with my map and the corresponding map pin icons.

I just created a few map icons, but they don’t appear on the map. The standard pin always remains.

Then I tried the function “Select a map icon, or pick a Font Awesome icon and color below to have one auto-generated. (If this field is empty)”.

With a single icon, it worked. Font Awesome created a map icon for the truck (fas fa-truck) and it is displayed in the backend. The map pin is red, but I can’t change the color either.

I tried numerous other Font Awesome Icons (fab fa-btc), but unfortunately without success.

But even the Truck Map Icon is not shown on my map.