The reason for an agent Line status being stuck, e.g. on "ringing" even though their phone does not ring is usually that their phone device or softphone was not registered or not available the last time they were called.
The same issue can occur if the agent tries to take the call on an end device (phone) but the call is not correctly established. It is possible to also get stuck on another Line status, e.g. "In-call" even though the call has ended. The reason therefore might also be that the end of the previous call was not correctly signalled or received.
The solution is quite easy: just wait a minute or two. babelforce automatically attempts to detect these spurious statuses and the agent's line status will return to "available". If the call is still stuck after a minute, please make an outbound call to 1000. This should reset the status.