On your QRZ page, you say you have an ic7300. You should be able to connect that directly to your computer with a USB cable. Maybe if you take the Signalink out of the loop, get that working and then go back to the 706. Some other random thoughts, only because I have done them. One time I forgot that the tuner was turned to my dummy load. Oddly enough, it could receive signals. I never received an answer. One time I left it on FT4. I've not paid attention and forgotten to tune for a new band. Receive was ok, but SWR was off the scale. I can't remember the option, but you can have different setups in WSJT-X and I accidentally switched to one where the audio setup was incorrect. I've forgotten to turn up the power on the radio. I'm sure that there are others. You could also try a different FT8 program other than WSJT-X. The only thing that I've used the Decode button for, is when I accidentally double click the Erase button and it erases both panes. If you click Decode, it will re-decode that last 15 second window of data. I'm not sure, but maybe if you change the decode type from Fast->Normal->Deep, it would decode using those options, but that seems pretty unreasonable for FT8. Maybe with JT65 when you have a minute between cycles. Anyway, maybe there is a setting for Decode, but mine always decodes automatically.