It’s because of the unicode character in your devforum post most likely. They should try and fix that so it supports URL-encoded unicode characters in the slug (named part of the link)
To work around it for now, can you try changing the slug, it doesn’t matter what it is since the forum will use the topic ID in the string and will still resolve correctly anyway. Try this for example:
Thank you for bringing this to our attention. This issue has been resolved and you should now be able to use DevForum links that contain URL-encoded Unicode characters in the title portion of the link.