Are you looking at the stats from the old URL?

If so, you need to add the new URL & give it a few days for the new reports to populate.

Did you do the proper 301 Moved Permanently?

I just updated the sitemap I think in webmaster tools. Should I have deleted the old site and added a new property?

Even if you modified your sit map, Google can still crawl old URLs. There can also be links from other sites, which are still referencing your pages.

If the change of the URL only involved rewriting , and not content removed, then you should set up 301 redirects.

(I hope I understood the problem)

I did set up the 301 redirect and its been present in htaccess since the change and it appeared to work, but when I click a link given in webmaster tools errors the site isn't redirecting.
Sorry if it's not explained very well.

So it sounds like a mistake in your htaccess rules, but since I am not using Apache, I can't really help on this matter.

I just updated the sitemap I think in webmaster tools. Should I have deleted the old site and added a new property?

Don't delete your old site... but yes, you need to add a new property (as I said above.) Give it a few days for the reports to populate, then use those reports from then on. Depending on how long ago you set up the 301, there may already be some report data present.

when I click a link given in webmaster tools errors the site isn't redirecting.

They are errors. Not important that they redirect since there may be mistakes in the path.

What *is* important is that all your old pages are properly redirecting to all your new pages.

And yes, a new sitemap.xml is important to let Google (and other SEs) know about your new page URLs.

when clicking the not found errors it is still coming across the old links which return 404 errors

Did you mean that when you yourself request the old URLs, you get a 404 response?

That, I grieve to say, is not a GSC/WMT problem. (And that's not something you hear every day.) It is a problem with the redirects at your site.

We will not talk about how long it took me to figure out why FF is showing the partial/warning/some-insecure-content icon. Urk.

Did you mean that when you yourself request the old URLs, you get a 404 response?That, I grieve to say, is not a GSC/WMT problem. (And that's not something you hear every day.) It is a problem with the redirects at your site.

If his errors are anything like the ones I see for the several sites I manage, there can be *anything* in those errors. I see all kinds of non-existent paths marked as so-called "errors" in GSC.

So as I said above...

Not important that they redirect since there may be mistakes in the path.

...whether *he* clicks them or not.

Now, if the paths are accurate from the old site then that's a different story and it would imply that either the 301 was not done properly - or - that the 301 did not include all pages. Of course maybe faceman did not intend for all pages to get the redirect... however 51k 404s is a lot of missing pages.

If I saw 663 "Access Denied" errors in GSC, I would be pulling those 403s from the access logs to see the requests. It is not clear what kind of "minor change" was made. The Soft 404s could mean a faulty rewrite that may be serving some unrelated content - or not.

You could get more specific and useful help in the Apache Forum [webmasterworld.com]