He then copied over the old 2.4 DB and moodledata folder and we ran the upgrade. It appeared to be successful (I am seeing the courses) except that we can't log in now.
Can someone provide a clue as to why this may be?
You might need to copy your password salt from the old config.php into the new one. While it may not be needed after everyone logs in once, if you had a password salt before, Moodle will need it to log people in until the password fields are updated not to require it.
Thank you! Thank you! That was exactly the problem.
Thanks for the quick reply!!