Digium Fax problems

I am trying to get an old analogue fax machine to work with Asterisk and a Digium analogue card and a SIP trunk. Everything works, including analogue phone calls, except faxes (and I have only tried outgoing so far). I have installed the Digium free fax modules and I can see this in the stats:

localhost*CLI> fax show stats

FAX Statistics:

Current Sessions : 2
Reserved Sessions : 0
Transmit Attempts : 0
Receive Attempts : 0
Completed FAXes : 0
Failed FAXes : 0

Spandsp G.711
Success : 0
Switched to T.38 : 0
Call Dropped : 0
No FAX : 0
Negotiation Failed : 0
Train Failure : 0
Retries Exceeded : 0
Protocol Error : 0
TX Protocol Error : 0
RX Protocol Error : 0
File Error : 0
Memory Error : 0
Unknown Error : 0

Spandsp T.38
Success : 0
Call Dropped : 0
No FAX : 0
Negotiation Failed : 0
Train Failure : 0
Retries Exceeded : 0
Protocol Error : 0
TX Protocol Error : 0
RX Protocol Error : 0
File Error : 0
Memory Error : 0
Unknown Error : 0

Digium G.711
Licensed Channels : 1
Max Concurrent : 0
Success : 0
Switched to T.38 : 0
Canceled : 0
No FAX : 0
Partial : 0
Negotiation Failed : 0
Train Failure : 0
Protocol Error : 0
IO Partial : 0
IO Fail : 0

Digium T.38
Licensed Channels : 1
Max Concurrent : 0
Success : 0
Canceled : 0
No FAX : 0
Partial : 0
Negotiation Failed : 0
Train Failure : 0
Protocol Error : 0
IO Partial : 0
IO Fail : 0

If I try sending a fax it gets so far but stalls at V.21 detect:

localhost*CLI> fax show sessions

Current FAX Sessions:

Channel Tech FAXID Type Operation State File(s)
SIP/spitfire-0000000 Spandsp 0 none V.21 Active
SIP/spitfire-0000000 Spandsp 1 none V.21 Active
SIP/spitfire-0000000 Spandsp 2 none gateway Active

3 FAX sessions

localhost*CLI> fax show session 0

FAX Session Details:

session : 0
operation : V.21 Detect
state : Active

Should the “Tech” not be Digium? But if I don’t load the spandsp module it gets even less far. I have turned on T38 support in the config files but not sure that is relevant at this stage. Also I noticed its using u-law rather than A-law which seems wrong too. Thanks.