Incoming calls ok, outgoing stopped working : 'All Circuits Are Busy Now'

R4FXO-EC
Asterisk 2.4.2
2 POTS lines plugged into ports 1,2 while 3,4 are unused. Incoming calls are fine while the outgoing attempts get the busy message. The setup has worked OK before this just started happening all of sudden. Can please somebody post some pointers how to troubleshoot this.

ztcfg -v output

Zaptel Version: 1.4.7.1-3259
Echo Canceller: OSLEC
Configuration
======================

4 channels to configure.

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asterisk -rx "zap show channels" output
Chan Extension Context Language MOH Interpret
pseudo default en default
1 from-zaptel en default
2 from-zaptel en default
3 from-zaptel en default
4 from-zaptel en default

*****************************************************

Using zttool :

Rhino RCB4FXO/1
Current Alarms: No alarms.
Sync Source: Internally clocked
IRQ Misses: 0
Bipolar Viol: 0
Tx/Rx Levels: 0/ 0
Total/Conf/Act: 4/ 4/ 2

1234
TxA 0000
TxB 1111
TxC 0000
TxD 1111

RxA 0011
RxB 1111
RxC 0011
RxD 1111

When we initiate an outgoing call the Tx side changes the Rx does not.

Thanks,

Gabe