500 errors – solved, now I get 404 behaviour

First I started to get 500 internal database error
so searched on GoDaddy Support for advice, followed the advice in
https://help.godaddy.com/article/1655

Now I get 404 behaviour, I can see posts on the main page, but if I click on any links on the main page that are internal to the wordpress part of the site, I get GoDaddy’s 404 page. e.g. if I click to see the whole of a post then the error occurs. This happens when I click to view Posts, Pages, categories, tags in the sidebars etc.

The Blog is at https://www.saltaire-aa.org/wordpress with a post explaining the problem to our members entitled “normal-service-will-be-resumed-soonlater” visible on the main page but not as a single post.

If I gave you the link to the post here you would see GoDaddys 404 page. I guess its some sort of file protection problem of a file in the series of files in processing the file to display it, but which file has duff protection or is really missing. I am fairly new to administering wordpress

Any help or advice appreciated.