[LG G6 Guides, News, & Discussion] badziewmax:
I have the same problem, first to fix perms problem I did

adb shell pm grant net.dinglisch.android.taskerm android.permission.WRITE_SECURE_SETTINGS

and then I got this:

11.30.27/E Java Function: ->
11.30.27/E Java Function use app context
11.30.27/JU analyse: target: android.provider.Settings$System expected: null
11.30.27/JU target: analyse done: android.provider.Settings$System: class: android.provider.Settings$System obj: null partWithoutMods: null static: true const false casted: false
11.30.27/JU analyse: returnval: boolean expected: null
11.30.27/JU returnval: analyse done: boolean: class: boolean obj: null partWithoutMods: null static: true const false casted: false
11.30.27/JU initClass: class: boolean obj: null partWithoutMods: boolean static: true const false casted: false
11.30.27/JU initClass: retnovar: init with array handling -> boolean
11.30.27/JU initClass: class: android.provider.Settings$System obj: null partWithoutMods: android.provider.Settings$System static: true const false casted: false
11.30.27/JU initClass: target: init with array handling -> class android.provider.Settings$System
11.30.27/JU analyse: param0: cr expected: class android.content.ContentResolver
11.30.27/JU param0: analyse done: cr: class: android.app.ContextImpl$ApplicationContentResolver obj: android.app.ContextImpl$ApplicationContentResolver@d290cb7 partWithoutMods: null static: false const false casted: false
11.30.27/E param 0 class: class android.content.ContentResolver
11.30.27/JU analyse: param1: enable_ext_display_on_lcd_off expected: class java.lang.String
11.30.27/JU param1: analyse done: enable_ext_display_on_lcd_off: class: java.lang.String obj: enable_ext_display_on_lcd_off partWithoutMods: null static: false const true casted: false
11.30.27/E param 1 class: class java.lang.String
11.30.27/JU analyse: param2: 1 expected: int
11.30.27/JU param2: analyse done: 1: class: int obj: 1 partWithoutMods: null static: false const true casted: false
11.30.27/E param 2 class: int
11.30.27/E targetClass: class android.provider.Settings$System
11.30.27/E object: null
11.30.27/E method: public static boolean android.provider.Settings$System.putInt(android.content.ContentResolver,java.lang.String,int)
11.30.27/E arg0 class android.app.ContextImpl$ApplicationContentResolver value android.app.ContextImpl$ApplicationContentResolver@d290cb7
11.30.27/E arg1 class java.lang.String value enable_ext_display_on_lcd_off
11.30.27/E arg2 class java.lang.Integer value 1
11.30.27/E Java Function: java.lang.reflect.InvocationTargetException
[B][COLOR="Red"]11.30.27/ Caused by: java.lang.IllegalArgumentException: You cannot keep your settings in the secure settings.[/COLOR][/B]
11.30.27/ android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:165)
11.30.27/ android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:135)
11.30.27/ android.content.ContentProviderProxy.call(ContentProviderNative.java:651)
11.30.27/ android.provider.Settings$NameValueCache.putStringForUser(Settings.java:1859)
11.30.27/ android.provider.Settings$System.putStringForUser(Settings.java:2274)
11.30.27/ android.provider.Settings$System.putIntForUser(Settings.java:2379)
11.30.27/E result: stop task (error)
11.30.27/E Error: 1
11.30.27/MacroEdit action finished exeID 1 action no 1 code 664 status: Err next 1

Marked is the problematic piece, I sadly do not know how to fix that.