I have a Toshiba TV with the Fire OS built into it.
It is running Fire OS 7.2.5.8 and Cinema HD 2.4.0 with Series Guide V57 DatabaseV48 and everything is fine I can see Cinema HD, CyberFlix, and CatMouse under my Customized Extensions. but I am setting up a 4K Max FireStick on one of the HDMI ports on the same TV and everything is the same except the Fire OS is 7.2.5.5 and I can see CyberFlix and Cat Mouse under the Customized Extensions on that system, but I can not see Cinema HD as an option to add under the Customized Extensions and Cinema HD is the player that I like to use the most.
Sorry, you would have to ask the developer of that extension to look into this.
As I don’t officially support Fire OS I don’t really know what the differences, even between point releases are. But others have reported similar issues with extensions and there is no known solution.