Using the Legacy API Key for Slack Integration is going to break at some point in the near future. Upgrade to either interact with Slack Incoming Webhooks, or create a Slack App to integrate with.
Welcome to the community. Thanks for the suggestion, we would definitely check that out.
It would appear that the Legacy API key are no longer available and the functionality is now broken
Welcome to the community @rbaffoe!
In this case you can now simply switch to OAuth2. The latest version of n8n already supports it.