moving Wp from install directory – What am I doing wrong??

My server provider is 1&1
I installed WP as a clean installation in its own directory. I use it as a blog
I run a prestashop website from another directory on the same server which is where my ULR point to
I want to run the WP blog from my shop so it has the same URL
my shop is https://www.knoticalbutnice.co.uk”

I created a new sub directory https://www.knoticalbutnice.co.uk/Blog and moved all my WP files there ( I have kept the original files in the original directory)

I have changed my WP DB to reflect this. Changed the settings in the BO to the new directory.
I have changed the index.php file to reflect the new directory
The prestashop module was also changed and BINGO my blog can be seen in my shop.
New post are also seen there
BUT
click on a post and I get a 404 error – no post
If I go back into the BO of WP and try to access my site from there, my page is there but the posts are not, they just turn up a 404 error again

Please help – what am I doing wrong?