If I set a transparency level for a point layer to 0 and use a standard heatmap renderer with default configuration in a webmap, the layer is still visible. While I am editing the ma, after I set the transparency of the layer to 100%, the layer is transparent. But if I reload the map in the map viewer, it is no longer transparent, even if the settings indicate that it is transparent.
I have found that I can make the layer transparent by first going to the heatmap style option and setting the transparency to 100% and then saving the map. This will change both layer and render transparency to 100% (identical to setting it at the layer transparency).
As a side note. If I chose a point renderer as opposed to the heatmap, this does NOT occur.
Here is a link to a map that displays incorrectly.
Here are two screenshots of the results of setting the layer transparency to 100%.
Transparency set at layer
The transparency was not set in the style but it was "automatically" set when I set the transparency level for the layer to 100%.