I would check to make sure that you’re sending to the right Slack email address, Slack username, or Slack user ID.
Note that the username is different than the display name, which often confuses people.
You can read more in Airtable’s support article here.
If you still can’t get it to work, post a screenshot or a video of your problem.
Also, you can always test your methodologies by using Make’s Slack automations for Airtable. If the same problem occurs there, then it’s something incorrect with how you’re sending the data to Slack.
If you’ve never used Make before, I’ve assembled a bunch of Make training resources in this thread. For example, here is how you would instantly trigger a Make automation from Airtable.
p.s. If you’d like to hire an expert Airtable consultant to help you with anything Airtable-related, please feel free to contact me through my website: Airtable consultant — ScottWorld