Blog Post Migration Problem

I have had a WP Site running for about a year. It was a main site and a blog all in one. But I wanted to have them separate so I could have distinctly different themes, one for the “static” site of pages about my business and the second just for a blog of posts.

I created a /blog subfolder on my main domain and created a new WP installation within that subfolder. Uploaded and customized my theme etc. for the /blog portion. Then I exported just the posts from the original site and imported them into the blog within the /blog subfolder.

Almost everything is working except that on the main page of the new blog site, only the first page of posts is showing up. If I click the “Older Posts” link at the bottom of the page, I am getting an error. The link is directing me to the main directory site with the message “Not Found. Apologies, but we were unable to find what you were looking for. Perhaps searching will help.” with a search box. And that error message is being shown on a page for the main site (with it’s design theme).

Thank you.