This issue can happen for Magento Cloud customers who trigger Blackfire builds at each deployment.
This means that at least step 3 of the configuration guide for Magento Cloud has been successfully completed.
Solving the issue
For each Blackfire environment you're working with for the Magento Cloud project:
- Browse to its "builds" tab
- Click on the "i" icon next to Magento Cloud in the integrations list
- Open the advanced settings
- Scroll down to and check the "Disable SSL certificates verification" option, then Save the settings.
User journey as below: