Posting this here in hopes that it helps someone else solve a similar problem.
My issue was: On a setup that was very well established for JT8, JS8, PSK31, etc, I was able to get everything working enough to be able to send out beacons and CQ's (only), but could not get any RF output once a connection was established. I went down many rabbit-holes trying to figure it out, but in the end it was very, very simple....the short answer is: go to Windows Sound Control Panel, select the device that is your Signalink OUTPUT (on my machine it was "5-USB AUDIO CODEC" on the PLAYBACK tab, right click on that device >> click Properties >> click the ADVANCED tab >> change the setting to "16-bit, 44100 Hz (CD-Quality)" >> OK >> OK
Once I did the above, setting the sound output format to 44100 Hz on the SIGNALINK OUTPUT, I was able to transmit and make QSOs just fine. I hope this helps someone!
73 de KG9NI
To get to Sound Control Panel on Windows 10:
Press Windows + R keys together to launch the Run dialog box.