As I said in another post, I upgraded my Alpha installation to Beta by uploading the files using FTP.
On another site, I thought I would try the migration from WP to CP Beta using the plugin.
The file is called upgrade-to-classicpress.zip which is confusing. For the Alpha migration, it was called switch-to-classicpress.zip which makes sense.
So I installed the plugin anyway and it said it was going to install the Alpha version?? It then hung, with that message:
Another update is currently in progress.
I logged out and logged back in again, but it gave me the same message. I then uploaded the Beta files via FTP instead, which worked.
I think the zip file is misleading and should be renamed. I also suspect it is actually trying to fetch the Alpha version (or the nightly build). I may be wrong, but please check that.
For a newbie to CP without the tech skills to play with backups and FTP, it could very well put them off, with a bad first impression.