Thank you for your post.
For testing purposes, can you try this using full access privileges? This may help me determine the next course of action.
I deactivated Guest account, edited Full Access to have extended priviledge so that only Admin now has full access. In PHP Site Assistant, after connecting the server, I chose the database and the system asked me to log in with Full Access credentials. I was able to log in as Admin but Choose LayOut group button is still grey.
I am having the same problem though with a version of PHP site assistant that has worked on the exact same database in the past. I have checked all security for the file inside and out and can get other files to work but not this one.