If you had already installed Signer version less that V 3.0, you will need to upgrade your database and move files. To know if you are using less that V 3.0, check if your installation uses config.php file instead of .env file to store system variables. We have created a post on how to upgrade easily. Check out this post https://simcycreative.com/how-to-upgrade-signer-to-version-3-0/
If you are updating from version 3.0 to greater version extract the zip files from CodeCanyon and copy the into your current installation except .env file on the root folder.
Check your database tables if you have a table called timezones, if not download timezones table from this link https://www.dropbox.com/s/kfee4b5hww8zbcj/timezones.sql?dl=0 and import it into your database. Once that is complete, login to your Signer account and navigate to your site /update for example https://example.com/update click on update now.
If the loading takes longer than a minute just refresh the page.