Not able to register system

Subscription - 3
Active - 2
Not able to register a new system
Error Message: ▒ │
│ Insufficient Software Channel ▒ │
│ Entitlements: ▒ │
│ ▒ │
│ cfid8960 Red Hat Enterprise ▒ │
│ Linux Server (v. 6) ▒ │
│ ▒ │
│ note: One of the above Software ▒ │
│ Channel Entitlement(s) are required ▒ │
│ to provides access to: cid10486 Red ▒ │
│ Hat Enterprise Linux Server (v. 6 ▒ │
│ for 64-bit x86_64) ▒ │
┌│ Error Class Code: 70 ▒ │
││ Error Class Info: ▒ │
││ All available subscriptions for ▒ │
││ the requested channel have been ▒ │
└│ exhausted. ▒ │
│ Please contact a Red Hat ▒ │
│ Network Sales associate. ▒ │
│ Explanation: ▒ │
│ An error has occurred while ▒ │
│ processing your request. If this ▒ │
│ problem ▒ │
│ persists please enter a bug ▒ │
│ report at bugzilla.redhat.com. ▒ │
│ If you choose to submit the bug ▒ │
│ report, please be sure to include ▒ │
│ details of what you were trying ↓ │
│