Allowing Box Drive in Security & Privacy doesn't "stick"

Box ended up coming back with the following. This worked as further described at the end. (In response to Viking: yes, I was using the most recent installer, which was intended for Big Sur.)

1. Quit Box Drive
2. Run the uninstaller script. Launch Terminal, then type the following: "/Library/Application\ Support/Box/uninstall_box_drive"
3. Check that the folder path ~/Library/Application\ Support/Box doesn't exist or is empty. Check that Box Drive has disappeared from System Preferences.
4. Restart the machine.
5. Install the latest Box Drive here. When prompted, enable the kernel extension from System Preferences -> Security And Privacy.
6. Attempt to manually load the Box Drive kext (no output will be displayed if it succeeds). Launch Terminal, then type the following: "/sudo kmutil load -p /Library/Filesystems/box.fs/Contents/Extensions/11.0/osxfuse.kext/". If it does succeed, please allow the kext through System Preferences and reboot.
7. Apple engineering team suggested the following workaround as National Instruments' kexts are causing problems. Delete /Library/Extensions/nipalk.kext, /Library/Extensions/ni488k.kext, /Library/Extensions/NiViPciK.kext (or any other National Instruments kexts). [I did not have these.]
8. Boot into Recovery mode, then launch Terminal, then type the following: "kmutil trigger-panic-medic --volume-root <pathToYourMacOSVolume>" (<pathToYourMacOSVolume> will typically be "/Volumes/Macintosh HD").
9. Restart the machine and let it boot normally.
10. Launch Box Drive, which should walk the user through re-approving the Box Drive kext. You will need to reboot once, possibly twice, to re-enable kexts.
11. If the above steps do not resolve, please collect Sysdiagnose logs for us to send to Apple. Launch Terminal, then type the following: "sudo sysdiagnose". When the command finishes, there will be a line that says "Output available at <file location>". Please send us that tar.gz file.

It was Step 8 that did the trick; the previous steps did not appear to have made a difference.

Thanks everyone. This is resolved.

Thanks for the suggestion. I have tried that and am greeted with the same behavior at the Test Admin new account.

Today Box support also suggested:

1. Boot into Recovery Mode

2. Reset SIP configuration by running the following in Terminal:

-csrutil clear

-csrutil enable

3. Restart

4. Try to install / use Box. A dialogue should appear asking the user to allow the Box kext and restart to be able to use Box.

That did not work. They have said they are escalating the issue within Box support, but have I have not yet heard anything more back from them.

In answer to your question, the exact sequence I get with Box is:

1. Box boots for first time, after start up.
2. Box opens a window: "macOS Installation. Please enable the Box system extension in System preferences..."
3. Click "Open System Preferences" on that Box window, opening System Preferences.
4. In System Preferences, click unlock, then click Allow.
5. The Allow button goes away and System Preferences pops up a window "A restart is required before new system extensions can be used." Choices are Restart and Not Now. Call this System Window 1.
6. After a short delay another window pops up, which also looks like a system window. "System Extension Updated. A program has updated system extension(s) signed by "Box, Inc." To finish the update, you must approve it in the Security & Privacy System Preferences." It gives OK and Open System Preferences as the choices. Call this System Window 2. In the background, the Allow button is now visible again in the Security & Privacy pane of System Preferences.
7. [Steps 4-6 can be repeated indefinitely by clicking either option in System Window 2 and Not Now in System Window 1, bringing you back to Allow.]
8. Reboot. Go back to Step 1. All other Steps occur as described above.

Note that if the Box App is manually quit before Step 5, Step 6 does not occur. Which is to say, the Allow button does not return. But it does not make a difference; rebooting still returns you to Step 1 and all Steps thereafter occur as described. Note also that very quickly clicking Restart on System Window 1 also does not help. System Window 2 pops up before the computer shuts down.