Can't add SmartThings ERROR: Something went wrong. Please try to install the SmartApp again

I’m trying to re-add smart things - It was working for me for a while and then I moved and I guess that broke something.

Now when I try to re-add it, SmartThings’s website gives me this error:

ERROR: Something went wrong. Please try to install the SmartApp again.

When I try and access my own web hook url, I get an error 405.

My HA install is hosted locally with a valid internal/external DNS name which resolves successfully outside my network. I’m using a current LE cert for SSL.

I’m pulling my hair out lately… everything I’m trying to do in HA is broken and I’ve been using HA since the very early days. I’d be grateful for any help. When I google these various errors, I get posts from 2019 and 2020 which are no helpful - a lot of the underlying things have changed. For instance, one fix is to remove a theme string from the Samsung url, but the current url doesnt have that theme string.

I’ve also run the hass_smartthings_remove and I’ve removed all apps with the smartthings cli tool. I’ve rebooted everything multiple times.

I’m running HA 2022.06

bump - anyone solved this? Seeing lots of threads but not many solutions.