You have to use new protocol (Protocol 2, or "P2") firmware to run Thetis on any radio.
P2 firmware for all radios can be found
here.All P2 firmware is late alpha/very early beta status. It may work, it may not work, or it may sort of work. If you've loaded it and nothing is working, switch back to P1 firmware and make sure all is well. If it is, it might not be working on your particular radio. Because of timing problems in the currently released alpha/beta P2 firmware, it is, for example, possible to try the same firmware on ten different 100D radios and watch it work on some and not on others.
When moving from P1 firmware to P2, you can use either HPSDR Programmer or HPSDR Bootloader.
When moving from P2 to P1, or from P2 to a newer version of P2, you can use either the
new protocol programmer or HPSDR Bootloader. I recommend Bootloader, it is easier and more reliable.
Instructions for using HPSDR Programmer and HPSDR Bootloader can be found
here.73,
Scott