First, check and see that the Thunderbolt device is being seen by the operating system.
Launch System Information (Applications > Utilities > System Information)
Click on the Thunderbolt/USB4 under Hardware:
You should see LT-TB or LT-TB3 listed under Thunderbolt/USB4. If not, check your cabling and that the device is powered up. If the cabling is correct and the device is powered up, on the LT-TB check that LED D30 is flashing; on the LT-TB3 check that LED D1 on the wrap-around board is flashing.
Next, check under PCI to see if the LT-TB or LT-TB3 shows up as a PCI device:
On this sample screen, you can see the LT-TB is showing up as pci1621,14 and the driver is not installed. It is assumed that you have already tried to install the driver, so you need to check the Kext_policy database to see if the driver is being blocked from loading.
Launch Terminal (Applications > Utilities > Terminal)
Here is the line you can cut-and-paste into Terminal:
sudo "/usr/bin/sqlite3" "/var/db/SystemPolicyConfiguration/KextPolicy" "SELECT * FROM kext_policy;"
As a short-cut, please see the attached "kextpolicy.zip" file attached to the bottom of this page. Simply open the zip file which will extract the script file "kextpolicy", then double-click on the kextpolicy script.
And here is an example of a sample of what you might see:
Each of the five fields are:
|Team ID||Bundle ID||Allowed||Developer||Flags|
|M3FXK28JC9||com.lynxstudio.driver||1||Lynx Studio Technology, Inc.||0|
The flags field can be:
|0||Driver is Allowed|
|1||Driver was upgraded, must be Allowed by the user in "Privacy & Security"|
|4||Driver is blocked from loading, must be Allowed by the user in "Privacy & Security"|
If your Macintosh is:
* Not loading the driver
* Flags ≠ 0
* Not showing the Allow button in Security & Privacy
You will need to delete the driver's entry from the database and reinstall the driver.
Normally, the kext_policy database is locked in read-only mode. To modify the database the Mac will need to be rebooted into recovery mode.
Booting into Recovery Mode:
Intel: Restart the Macintosh. Hold down the "COMMAND ⌘" and the "R" key until the boot chimes play.
Apple Silicon M1: With the Macintosh off, hold down the power key and continuing to hold down the power key until the recovery environment starts.
Once recovery Mode has loaded, click Utilities, and select Terminal.
In Terminal, type (where Macintosh HD is the name of your boot volume):
"/Volumes/Macintosh HD/usr/bin/sqlite3" "/Volumes/Macintosh HD/var/db/SystemPolicyConfiguration/KextPolicy"
Once sqlite is running type the items in bold (being careful to type EXACTLY what is shown):
sqlite> DELETE from kext_policy where Bundle_ID = 'com.lynxstudio.driver';
Then from the terminal prompt, type:
Restart the Macintosh.
Run the "Uninstall Lynx Driver" application to remove the current installation of the driver.
Restart the Macintosh.
Install the driver.
Make sure to click "Open Security Preferences" after the driver has installed.
Next click "Allow"Restart the Macintosh once again.
Double-check that the driver is now showing as installed in System Information: