Alexa won't allow certain types of devices to be controlled not sure if a Fireplace is one of them as I don't have one.
If that is the case, however, you can work around it. Set up a virtual dimmer and call it Bedroom Fireplace. Then setup up a RM rule that when you set the Virtual dimmer to a level it passes that level to the actual fireplace in HE.
Have you used the remotec zfm-80 with any other device? If so, does it work properly? I have a generic ZWAVE device that turns my fireplace on/off with Alexa commands.
I have resolved the sneaky issue. The problem was that Alexa had ingested the devices from my old (non-Hubitat) hub, and then leased the new devices from Hubitat. So Alexa had duplicate entries for identical names, half of which no longer existed.
I had to remove all the old entries from Alexa's list through the Alexa app (Devices/All Devices). Annoyingly, each item had to be removed separately, complete with a confirmation, rather than a way to easily choose and delete multiple items. But Alexa is now working as expected.
Alexa will also take some liberties and create multiple entries for a new device that can have different connection options. The biggest headaches for me are non-Hue bulbs on a Hue Bridge. For instance, a Cree bulb on the Hue bridge nets Alexa devices "Connected via" Philips Hue Electronics, Signify Netherlands B.V., Cree, and Bathroom Dot. (If I shared through the Hubitat Alexa Skill, that would make another.)
Three of those four have to be disabled for voice commands to work. If they are deleted , they will reappear the next time any device discovery is done.