Turn off connectivity checks on android. Error with adb

Question

Hi I'm trying to turn off connectivity checks on android as detailed here: https://mullvad.net/en/help/configure-connectivity-checks-on-android

When I run the command highlighted in bold I get the following error.

Can anybody explain how I can fix this and turn off the connectivity checks. Thanks in advance. I'm a novice so it's difficult for me to find help and understand a lot of it.

* daemon started successfully
PS C:\...\platform-tools_r35.0.0-windows\platform-tools>

.\adb shell settings get global captive_portal_mode
null

.\***adb shell settings put global captive_portal_mode 0***

Exception occurred while executing 'put':
java.lang.SecurityException: Permission denial: writing to settings requires:android.permission.WRITE_SECURE_SETTINGS
        at com.android.providers.settings.SettingsProvider.enforceWritePermission(SettingsProvider.java:2329)
        at com.android.providers.settings.SettingsProvider.mutateGlobalSetting(SettingsProvider.java:1473)
        at com.android.providers.settings.SettingsProvider.insertGlobalSetting(SettingsProvider.java:1427)
        at com.android.providers.settings.SettingsProvider.call(SettingsProvider.java:455)
        at android.content.ContentProvider.call(ContentProvider.java:2533)
        at android.content.ContentProvider$Transport.call(ContentProvider.java:530)
        at com.android.providers.settings.SettingsService$MyShellCommand.putForUser(SettingsService.java:382)
        at com.android.providers.settings.SettingsService$MyShellCommand.onCommand(SettingsService.java:278)
        at com.android.modules.utils.BasicShellCommandHandler.exec(BasicShellCommandHandler.java:97)
        at android.os.ShellCommand.exec(ShellCommand.java:38)
        at com.android.providers.settings.SettingsService.onShellCommand(SettingsService.java:50)
        at android.os.Binder.shellCommand(Binder.java:1054)
        at android.os.Binder.onTransact(Binder.java:882)
        at android.os.Binder.execTransactInternal(Binder.java:1290)
        at android.os.Binder.execTransact(Binder.java:1249)

I tried to turn off connectivity checks, I believe I ended up with an error that didn't allow this to happen but I can't find anything about this error online.