Magento 2.1.18 is the final 2.1.x release. After June 2019, Magento 2.1.x will no longer receive security patches, quality fixes, or documentation updates.
To maintain your site's performance, security, and PCI compliance, upgrade to the latest version of Magento.

Error after logging in to the Magento Admin

Details

The requested URL /magento2index.php/admin/admin/dashboard/index/key/0c81957145a968b697c32a846598dc2e/ was not found on this server.

Note the lack of a slash character between magento2 and index.php in the URL.

Solution

The base URL is not correct. The base URL must:

Start with http:// or https://
End with a slash (/)
Match the case of the web/unsecure/base_url record in the core_config_data database table

Re-run the installation using a valid value.

May 31st, 2019