Troubleshooting Lindy Slack Integration API and Channel Configurations

i have Lindy that is supposed to trigger on slack message and interact further in Slack. but I get error about API / channel configuration, even though it is simple and should be fine. in Lindy I can see messages in slack when I try to run a Test but it cannot reply in the channel and the workflow gets stuck. is this problem about the slack channel configuration *in slack* not in Lindy?