Although there is claim for Support on Basecamp-3, it is not through the Basecamp and Slack Zap. At the point where I need to authenticate to Basecamp from the Zap, I get the following error (below SS) and it blocks me from going forward. I have looked at many articles on the community and help site. Nothing fits the bill. Can I get a definitive answer?
Thanks in advance.
Hi
Welcome to the Community.
If you're having trouble with your Basecamp three to Slack integration, follow the correct setup steps: select Basecamp 3 as the trigger, connect your account, and then link Slack as the action app. If authentication issues arise, check your credentials, ensure Zapier has the necessary permissions, clear your browser cache, or try a different browser. If your organization has restrictions on third-party apps, you may need admin approval. If the issue persists, sharing error details will help troubleshoot further.
Thank you. Checking again with Basecamp. Turns out the Basecamp version that we are accessing is v2. I decided to take a lazy shortcut for now and use email to slack channel built in feature to post anything that comes from notifications@basecamp.com. Works.
That’s awesome
If you have any other questions, please don’t hesitate to reach out to the Community. We’re always happy to help! 
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