Upgrade results in "Public site is unavailable until the upgrade completes."

We have an existing Omeka 2.3.1 installation. Rather than upgrade in place, I created a new Omeka 2.4 folder and copied db.ini, files, plugins, and customized themes to the new folder.

This resulted in a

Public site is unavailable until the upgrade completes.

message when the page is visited.

Some online research indicated that this meant the database needed to be upgraded, so I created a new database, mysqldump'ed the data from the old omeka database to a file, configured the new site (e.g. set up a superuser, etc), and then sourced the sql dump file to the new database.

Now I'm once again stuck at the Public site is unavailable until the upgrade completes.
message. The documentation suggests that

If a database upgrade is needed, you'll automatically be redirected to an upgrade page (example.com/admin/upgrade). Click "Upgrade" to update your database to reflect the new data model and finish the upgrade

However this is not happening. Any suggestions on what I can to do make the new install functional?

It's not extremely accentuated, but the instructions tell you to go to the admin interface. Is that where you're going (/admin, not the front of the site)? You get that message on the "public" side but on the admin you should be redirected.

I'd also probably drop everything in your "new" database and just re-import the dump of the old one. The upgrade is designed to work against the old database as-is. You don't want to make a new install and then dump the old data on top of that.

Thanks! Going to the admin interface resolved the issue. As for dropping everything before importing the data, as far as I can tell, when you make a mysqldump file the first instruction for each table is

DROP TABLE IF EXISTS omeka_collections;

etc., so it should be adequate to restore from this SQL file.