For a clean CiviCRM reinstall under Ubuntu / LAMP / Wordpress to work, the initial clearing of all CiviCRM related files is essential. If there are any vestiges of a prior installation left, the reinstall will certainly fail (either with an Initialization error, or the "You do not have sufficient permissions..." error).
Here are the necessary steps to reinstall (not upgrade) CiviCRM, using the desired / most recent version.
1. Review the directory structure to be sure it is as specified. OK.
1. Get to the proper directory:
(for my configuration: var/www/wordpress/wp-content/plugins/).
2. Remove all civicrm files and folders:
sudo rm -R ./civicrm
3. Remove civicrm log and cache files and folders:
cd ./files
sudo rm -R ./civicrm
4. Remove the civicrm.settings.php file, if present from prior work.
cd ../civicrm
rm civicrm.settings.php
5. Check the wp-content/uploads directory for a civicrm subdirectory and files;
remove if found:
cd /var/www/wordpress/wp-content/uploads/
ls -al
(check for civicrm directory and files and remove if they exist)
sudo rm -R ./civicrm
2. Use wget to pull down the desire / most recent zip file. OK.
3. Unzip the file. OK.
4. Use sudo chown to set file ownership as appropriate. OK.
5. In your favorite browser, login to Wordpress and check the Wordpress plugins list to see if the CiviCRM plugin shows up (you may have to refresh the window). OK.
6. It does, click the Activate button. OK.
7. Activated. OK.
8. Navigate to: https://yourwebsite.org/wp-admin/options-general.php?page=civicrm-settings
9. If success, you can now see the installation page.
10. Click the configure CiviCRM button and get the green bar screen! OK.
You have now reinstalled CiviCRM. From here, follow the CiviCRM how-to for configuration details.