Our vendors providing calls had blocked our account for too many retries for a phone number which was not reachable.
Thankfully, we have been working on getting vendor-agnostic for these tough times. Thus, we have immediately moved to another vendor but this ended in disabling inputs on phone calls for the last 24 hours.
We have now fixed this issue. This means on a phone call, you can continue to take actions like -
press 4 to acknowledge
press 6 to resolve
press 9 to escalate