The "Invalid credentials" error occurs because your Clay API key is either incorrect or missing. Here's how to fix it: 1. Get your Clay API key by following this guide.
2. Go to the Integrations section in Clay and add/update your API key to your integration account.
3. Save your changes and try the Write to Table action again.You can find your Clay API key under Settings > Connections > search for Clay.
Source:Write to table integration overview | Documentation | Clay University