I'm having connection issues between Cloud Integration Gateway (CIG) and the ERP system.

Please follow the Troubleshooting CIG Connection issues Guided Answers.

Misconfiguration in one of the involved components.?

SAP Integration Suite Managed Gateway > Managed Gateway for Business Network
SAP Integration Suite Managed Gateway > Managed Gateway for Business Network SCC > Managed Gateway for Buyer Business Network SCC
SAP Integration Suite Managed Gateway > Managed Gateway for Sourcing Integration
SAP Integration Suite Managed Gateway > Managed Gateway Foundation & Tools > Managed Gateway for Managed Gateway Portal