Awesome!
Once again I apologize for the issue you experienced not being able to dismiss the notification I have a few things that would help me prevent this issue in the future
1. if you could share how you fixed the issue it would be great. From what I can tell it seems like an issue outside of my control and if not I would like to update it.
2. If you could share the theme it came recommended with I would like to contact the author to investigate further so this does not happen again. Preferably the authors support information if you have it.
3. I would be interested to know if this is a single or a multsite install I ported the notification from another plugin that is basically all notifications. I have never experienced an issue with multsite but I honestly did not test it.
I find it odd that the first URL you posted uses https://halinasplace.com.au/ which 404s which instead it seems it should be https://imagery.halinasplace.com.au/ I could be wrong. It seems to be redirecting on the front end correctly but not on the backend. I am guessing you are using Cloudflare at some point to do this redirection I could be wrong might of just been an ad when it 404s.
I am going to go through the steps I do to get the URL to dismiss the notification this may not benefit you personally now but it is nice to have it spelled out in the open. I get the request URI, which should be the part after the URL which should be something like /wp-admin/post.php?post=33&action=edit and trim of the /wp-admin. Then I use the admin URL to build the URL for the dismiss link. It seems to me something is filtering the admin URL or altering your URLs in some sort of way. Since I do not have access to your site I am just making a guess.
I would suggest to definitely double check your home and site URL in Settings > General and make sure both are set to https://imagery.halinasplace.com.au. Also when weird things happen URL wise it is beneficial to update your permalinks in Settings > Permalinks. I personally do not do any type of rewrites but it could be in a theme/plugin that did not refresh the permalinks on activation.
Thanks,
Dan