if you are having issues configuring your Io4K or other Thunderbolt/PCI/E AJA devices these steps may be helpful to you:

Have you tried a different thunderbolt cable or a different Io4K on the same computer?

Here are some suggestions to try:

To Reset the Io4K:
1) Remove power from the Io4K.
2) Insert a straightened paperclip into the small hole to the left of "LTC In" BNC and hold in place.
3) Power the Io4K and remove paperclip.
4) If detected by AJA Control Panel: go to firmware and reprogram firmware.
5) Power-cycle the Io4K

If Mac is running High Sierra 10.13.x. The OS may block system extension signed by AJA Video System "
OSX will show System Extension Blocked" As a result the AJA Control panel is RED although system
report under Thunderbolt still shows  AJA device connected.

To Resolve:
*       Open System Preferences
*       Select Security and Privacy
*       Under General tab check for Allow button for AJA device

Additional Troubleshooting:
If you do not see Allow in the Security & Privacy General  area Clear the AJA preferences in the Users & Root level; uninstall the AJA driver Restart Install AJA Retail installer again Check Security & Privacy after AJA install restart

*       You can clear users AJA preferences using AJA control panel -> presets: click on <erase preferences>.
*       Manually delete root level preferences from Mac HD:/library/preferences/ com.aja.* files.