System extension blocked

Try closing the System Prefs, click on one of the Ok messages, then Open System Prefs.

How are you running High Sierra and have the "Anywhere" option in the Gatekeeper settings?

Perhaps whatever is making that appear is interfering with the Kernel Extension approval message.

That setting has nothing to do with blocking extensions, and setting it is completely unnecessary as you can just control-click on an installer and select Open to bypass Gatekeeper's restrictions.

Try reinstalling the software and try enabling it again when you get the blocked message. You have 30 minutes to approve the kext. If you fail to approve it in that amount of time, the blocked message will reappear, but you won't be able to approve it. You'll have to reinstall the software to reset the 30 min timer.

The last part of the link is where I found the info on the time limit. You only have 30 minutes to approve. If you don't it won't show the option. It may be that reinstalling isn't enough to trigger the new timeout.

You could use the spctl command to either manually add those items to the allowed list, or disable it completely.

spctl help

will show you how to use the command. The kext-consent commands need to be run from Recovery.

I don't know the format of the team id which is needed to allow the kexts.

No, I can't help beyond how to use the command beyond what the help file describes.

As indicated, the spctl kext-consent command needs an Action argument. They are listed below the command.

For example, spctl kext-consent status will show you whether the consent is enabled or not.

Terminal is an option in the Utilities menu on the Recovery main screen.

The Tech Note I linked before explains where the Team ID comes from, but doesn't give an example of how the two parts are combined.

What else ?

That's all I've got short of suggesting you contact the kext developers.

This is the reference to what is happening: https://developer.apple.com/library/content/technotes/tn2459/_index.html

Try undoing the change you made.

sudo spctl --master-enable