I've been searching here as well as in Google for any answers. I've seen a thread or two randomly on other forums, one was a VZW customer who apparently found from their customer service, that there was a known issue on some devices and the fast wireless charging option was removed. Not sure if this was in a series of production, maybe earlier production devices? That specific thread was from the beginning of Dec 2017.
I've really found no concrete answers, and actually don't get anything when I search that is specific to Cricket Devices. I've got an ATT S8+, and I have the option and actually use fast wireless charging every night.
Hoping someone knows a way to force it back, or if this is something to be fixed by Samsung?
***EDIT - I just realized that my boss doesn't have fast wireless charging either, she hasn't been able to use the fast charger we got her for Christmas. She has a Vzw S8+.