/wp-admin redirects to main blog page

Hello all,
After several successful WordPress installations, I have come across my first small problem. I migrated a WordPress blog from a shared hosting provider to a virtual private server as part of a larger site upgrade. I was able to do this successfully except on thing… when I go https://www.mysite.com/blog/wp-admin and log in, rather than being brought into the admin interface, I am redirected back out to the main page of the blog, yet the https://www.mysite.com/blog/wp-admin address is still showing in the address bar. I can tell I am logged in and if click “edit this” within a post, I can successfully get into the admin interface.

Something must happening with whatever redirection happens when you typically visit /wp-admin and I think it must be something about the Apache web server configuration because to test, I installed a completely fresh wordpress install and had the same issue with the fresh install. Everything else seems to work fine.

Any ideas are much appreciated!