I experienced the same issue. Non-active features do not appear in grayscale. As a workaround, I duplicated the layer in the map and configured it to display the way I wanted in the app. In my case, I turned off the "Enable Time" option for the duplicate layer and applied a grayscale effect to replicate the desired setup. There are a few additional things we need to do as well, such as enabling or disabling pop-ups to avoid conflicts between the two layers, making one layer slightly transparent etc.
