Custom plugin does not send test alert

[imavroukakis]

I've forked an MSTeams plugin I found and tweaked it a bit

https://github.com/imavroukakis/cabot-alert-msteams

I added my repo URL to plugin-requirements

cabot_alert_email==1.4.3
cabot_alert_hipchat==2.0.3
cabot_alert_twilio==1.3.3
cabot_alert_slack==0.8.3
cabot_check_cloudwatch==0.1.2
git+https://github.com/imavroukakis/cabot-alert-msteams.git

and enabled it in the environment

CABOT_PLUGINS_ENABLED=cabot_alert_email,cabot_alert_msteams

Once I bring up all services via docker-compose I can see the plugin page

However, when I send a test alert, nothing appears in the channel and I don't even see the log statements. What am I missing?