... but be sure that the "LAN" box is checked on UISS.
There is a document at http://www.ariss.org/contact-the-iss.html which includes a step by step method of switching UISS from interfacing to the AGWPE to interfacing with the UZ7HO Soundmodem program.
The direct link is as follows to save searching the whole page: www.ariss.org/uploads/1/9/6/8/19681527/k9jkm_2012_symposium_ver2.pdf
When the ISS is running the HT there are often many packets that sound "good" but won't pass the checksum. I also test on 144.390 but those signals often are S9+40 while a good downlink from the HT on the ISS is S3 to S5, at best, on my station during closest approach. Often at AOS and LOS it is S0 but audible.
When I run a hardware TNC with PASSALL = ON it will display all the packets and there are many with errors but with enough information that you can understand the message. But I see lots of incomplete packets.
-- 73 de JoAnne K9JKM k9jkm@amsat.org