Civi 5.15.1, WP 5.3.2
We are in the process of upgrading Civi from 5.15.1 to 5.21, and are stuck at the "Upgrade the database" step in the upgrade instructions here: https://docs.civicrm.org/sysadmin/en/latest/upgrade/wordpress/
The first time we pasted the upgrade URL into our browser, we got a message saying our PHP version was out of date. So we upgraded it to version 7, and tried to reload the upgrade URL. Instead of an "Upgrade screen", we got the WP login page. Upon logging in, the WP Dashboard appeared, without any Civi upgrade button. Nor does the WP Updates page list Civi as an option.
We backed up our database before starting the installation -- should we just restore it, or are there other steps we should take first?
EDIT: We performed the above actions using Firefox 72.0.1 with the Standard Browser Privacy settings, but can make changes if need be.