Syrinscape Online comes in two parts, the Master Interface , which is the browser page used to trigger the sounds and Online Player, which is the app that allows you to play the sounds. The message that you are showing above suggests that you are not running the Online Player (or that there is an issue with the Player), so there is nothing to actually playback your sounds.
If you look at the message showing on the Control panel, underneath that error banner it’s showing that you currently have two devices linked, your computer and your android device. it also tells you “Only one linked device can be active at a time” Only the device that you want to play the sounds should be linked, so you will need to click the unlink button next to the one you do not need. Each Syrinscape account can have one linked device at at time, so you would have one device so you can hear your sounds and each of your players can link one device so they can hear the sounds. Does that make sense?
Full details for setting up and running Syrinscape Online can be found here https://www.syrinscape.com/online/ Follow the three steps to get it set up and linked and THEN try triggering the sounds from the browser
You may also find this tutorial video helpful; https://youtu.be/vfdider-rOQ