Ensure in your Audio MIDI application that "Device is Online" is checked and that the name field is left blank.
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There has been a reported error of the Mackie protocol in the MIDI Plugin.
Try this Beta it should fix the Problem from the Developer.
https://trevligaspel.se/streamdeck/midi/assets/se.trevligaspel.midi.3.1.0.452.zip
Unzip and double click to install