Duplicate Titles & Descriptions

Hi,

Google WMT is reporting duplicate title tags and page descriptions. I would love to get rid of them, but have no idea how.

Several are in directories that do not exist, some are caused by tags that no longer exist and several are caused by a permalink change from /day/month/year/title to just /title.

I have read about using Canonical links, but if the page causing the issue does not exist I can not insert any code.

I have tried using a soft redirect in the htaccess file to redirect links from the old permalinks to the new (as per the Yoast guide https://yoast.com/change-wordpress-permalink-structure/), but this has not worked.

I have generally tidied up and deleted all un-used tags and also made tags ‘nofollow’. Despite this, many are still being picked up as duplicates!!

Help!

T23