Shortcodes play an integral role in WordPress and Oxygen is no exception. When developing in Oxygen, your changes are stored in shortcodes and then rendered on the front end into HTML, CSS, etc when the page loads on the front end. Oxygen's code block element allows you to run any custom PHP inside of it, so that poses a risk if another plugin or WordPress itself experienced a security vulnerability that allowed it to execute shortcodes, your site could become compromised through Oxygen's shortcodes.
To remedy this, Oxygen has a shortcode signature feature enabled by default. These signatures help prevent unauthorized shortcodes from rendering on your site and help prevent a vulnerability from having a more substantial impact on your site than it otherwise could.
Generally, there's only a few circumstances where resigning shortcodes is necessary. Moving your Oxygen site from one domain or host to another will typical require you to resign, which usually doesn't take long depending on the quantity of content on your site.
Resigning shortcodes can also be done as a troubleshooting step if you're experiencing problems with your site that you can't seem to pinpoint.
If you're having an issue with your Oxygen site, there's a good chance resigning your shortcodes will fix it.