Quickly creating an issue for this; proper issue summary will follow.
https://www.drupal.org/docs/8/upgrade/upgrade-using-web-browser#pre-upgr...
If the database credentials to your source database are correct, the upgrade review page will appear as illustrated in the screenshot below. This page shows a summary of the upgrade status for all installed modules on the old site.
Latest iterations use this help text instead:
The new site is missing modules corresponding to the old site's modules. Unless they are installed prior to the upgrade, configuration and/or content needed by them will not be available on your new site. Read the checklist to help decide what to do.
GitHub Issue #:
3577
Recent comments
You may need to re-install your Backdrop site and restart the import after a failed import. While I've never used that module, rolling back the import may not be enough. I would be sure to have...
Importing Posts/Pages from Wordpress
Thank you for the willing to help. I am using WordPress import module to migrate posts and pages.
Importing Posts/Pages from Wordpress
What are you using to import?
Importing Posts/Pages from Wordpress