Even though I strongly agree with the resetting password suggestion, this is how you can enable plugins directly through the database:
1. Connect to your database server and select your Q2A database
2. Edit the following SQL statement by replacing qa_ with the appropriate table prefix you use and the correct plugins you want to enable
UPDATE `qa_options`
SET `content` = CONCAT_WS(";", `content`, "plugin-directory-1", "plugin-directory-2")
WHERE `title` = 'enabled_plugins';
Just to clarify: this SQL statement will enable plugins located in directories qa-plugin/plugin-directory-1 and qa-plugin/plugin-directory-2
3. Execute the SQL to enable the plugins