Hi @gcincilla,
it is an issue known to Indigo. It does not work for MacOS.
See Update of Indigo Knime nodes 路 Issue #762 路 epam/Indigo 路 GitHub
and a forum post talking about this issue: Cannot load indigo plugin
You could also raise awareness on GitHub (first link), maybe that helps them re-prioritizing it 
Best regards
Steffen