The steps I’m describing are supposed to run on a copy of your apparently-working, but incompletely-upgraded, production installation. You can (and should) use a copy of that, but I suspect you’re running these steps on an old backup of your 2.x database, which is not what I intended (and won’t work).
Regards,
Alec Smecher
Public Knowledge Project Team
What version of OJS does your production site claim to be running? By my understanding from this post, it reports 2.4.8-4.
If that’s the case, then you should be able to run this query on a copy of that database to force OJS to think its database was fully upgraded to 3.1.2-1:
UPDATE versions SET major=3, minor=1, revision=2, build=1 WHERE product='ojs2' and current=1;
If you get an error from that query, please double-check what’s in your versions table with product='ojs2' and current=1'.
Regards,
Alec Smecher
Public Knowledge Project Team