I am new to digital HF. I am using an early FT-817 with W-SJTX or JSTX and experience the same issue, that has me stumped. I am able to use FT8 without any issue, but FT4 just does not work. I have tried changing settings and levels, with no success. The interface is Rigblaster Plug And Play (6 pin data jack) with USB soundcard.
I am using the following: PKT RATE 1200 DIG MODE USER-U DIG DISP 0 DIG MIC 12 DIG SHIFT 0
I saw a post where someone said to adjust menu #55 USB offset, but my radio goes to #51.