Cannot create Space after upgrade to 7.3.1

[George I. Develekos]

Hello,

After an (otherwise) successful upgrade from 5.7.1 to 7.3.1, I see that I can no longer create spaces of any kind (Site of Personal), getting an "unknown server error". 

DB is MySQL 5.6.46.

As a sidenote, after the upgrade I had to rebuild the content indexes since spaces were visible but the space directory was empty. Now all spaces look fine.

I found on this site a "popular" solution that involved dropping 3 tables from the DB, deleting a few cache folders and bouncing Confluence. That didn't work for me, I still get the same error. The 3 tables were
 AO_54C900_CONTENT_BLUEPRINT_AO
 AO_54C900_C_TEMPLATE_REF
 AO_54C900_SPACE_BLUEPRINT_AO 

The error that appears when I try to create a space is:

==> atlassian-confluence.log <==
2020-02-29 16:43:16,908 WARN [http-nio-58090-exec-8] [confluence.impl.hibernate.ConfluenceHibernateTransactionManager] doRollback Performing rollback. Transactions:
->[PluginReadWriteTx]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT (Session #1160819858)
-- referer: https://confluence.cdialogues.com/spacedirectory/view.action | url: /rest/create-dialog/1.0/space-blueprint/dialog/web-items | traceId: e0b005b0764701e8 | userName: g.develekos

Please advise.

[George I. Develekos]

My apologies, I figured it out, it was a faulty setting in the database.