It depends on your hosting/server configuration. In most cases, the error log is usually accessible from the cpanel. If you have a dedicated server, you can find it under the web server log folder.

Try to reinstall the package again, and check that redj tables exist on the database. I would like to support you with this issue. If you agree, send me a private mail at info(at)selfget.com and we can use Team Viewer to fix the issue together.

Kind regards,
Luigi