Your topics are different. The outgoing is “sunroom/plug1” and the incoming is “/sunroom/plug1” (note the leading /).
But you have a bigger problem that will occur once you do fix that. You will have an infinite loop because when you send a message to the topic the Item will read in the new state as a command and then publish the new state as a command to the topic and then read the new state as a command …
Change “command” to “state” so when you read in the new state from the topic it will only update the Item’s state and not go back out to the MQTT binding and publish a new message to the topic, thereby cutting your feedback loop.
Usually users will separate the command and state topic so you can, for example:
Switch SmartPlug "Lamp [%s]" <poweroutlet> {mqtt=">[mqtt:sunroom/plug1/cmd:command:*:default],<[mqtt:sunroom/plug1/state:state:default]"}
which makes it even more difficult to accidentally fall into these sorts of feedback loops. It also makes it clear where the information is coming from. For example, the messages that get published to the state topic are coming from the device and those on the cmd topic comes from OH or anything else you have that can command the device. As a result, the state topic can become a sort of acknowledgement that the command was acted upon, in addition to capturing manual triggering of the device.
A Number Item or a String Item can have any number of values and on the sitemap you can use a Selection or Switch with mappings. I’m not sure what is the equivalent on HABPanel.
I don’t think Alexa supports such free natural text processing. I suspect you will have to say “Alexa, turn on PS4” and you will have to have a PS4 Switch Item tagged as switchable (or what ever Alexa uses) and a Rule to do all the actions that should occur.
Please use code fences for all code. How to use code fences