Service Temporarily Unavailable Error Appears after install extension

[Zoe Hell]

I am not even able to open the admin page or see any sort of errors on the page. If I visit any URL of my Magento site I am getting the above output.

Service Temporarily Unavailable

The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

How do I resolve this?

[LitExtension Expert]

To fix 503 Service Temporarily Unavailable Magento 2 error:

Go to the Magento 2 root directory and delete the .maintenance.flag file in the var folder.
Clean Magento cache from admin panel or by running this command:

php bin/magento cache:flush
php bin/magento deploy:mode:set developer
php bin/magento setup:upgrade