Echo only recognizes a very few device classes for the connected home category, basically lights and switches. Although it may be that you hadn’t authorized echo to see it.
There are two separate things you can try.
First, take a look at the echo FAQ (this is a clickable link) to make sure you’re authorizing the devices from smartthings to echo:
Next, if it is a device class that echo doesn’t recognize, you can still use the IFTTT integration to access it. See the first post in the following project topic. Although this particular topic is discussing harmony, that IFTTT method is the same for any smartthings device in the SmartThings IFTTT channel. So it’s an easy way to get past the device class restriction.