PCIe driver not running under macOS / System Extension blocked

While installing the driver of our Juli@ XTe, MAYA44e, MAYA44 XTe or MAYA44 eX under macOS 10.13 (High Sierra) or higher, it is possible that you receive the following message:

A new security feature in macOS prevents the loading of so-called "System Extensions" like our driver for the PCIe hardware. This message might be hidden after a while, especially if you reboot your system when the driver installer requests you to restart.

To make sure the driver is actually loading, go to your System Preferences and select the Security & Privacy > General panel there:

Make sure to click the Allow button next to the notification about our driver there.

If this button is not displayed (it might disappear after a while, especially if you install different system extensions after each other), then uninstall the driver again (which requires a reboot), then install it again and go back to this dialog in the System Preferences before you reboot your system then.