I voted to close this post as a duplicate of this other post recently, and the OP agreed with the close vote about an hour ago. Unfortunately, for some reason, the duplicate target header just reads "This question already exists:" with no link to the duplicate target. Here is a picture in case this issue is specific to me:
This seems like a bug, so here I am making a bug report. For reference, this other question was marked as a duplicate 10 hours ago and displays all the expected behavior for me - namely, the link to the duplicate post actually shows up on the page.
EDIT: As Xavier Henderson/Martin R point out, this is a known bug on the StackExchange side. Here is a post on the StackExchange meta site dealing with this issue.
EDIT 2: Asaf Karagila has used moderator powers to fix this specific instance, but the underlying bug is still active, per the meta.stackexchange post referenced in the first edit.