500 internal server error popped up when adding on Smartthings

I have successfully added “Nabu Casa” for cloud service and I am now able to access through ‘https://xxxxx.ui.nabu.casa’.

But the ‘500 internal server error’ message was popped up when I tried to add on Smartthings.

I think I already had ‘https’ from Nabu Casa.

How can I figure this out?

Please help…this drives me crazzyyyy…