You can generate up to three evaluation licenses for Confluence Server apps. If your draw.io evaluation license has expired you can get a new evaluation license through Atlassian.

1. Go to https://my.atlassian.com/products and log in with the account that has the evaluation license that just expired.
2. In the list of licenses or SENs on that page, find and expand the entry for draw.io Diagrams for Confluence: Trial.
3. Underneath the License Key field, click on New Trial License, and follow Atlassian’s instructions. Copy the license key that you are given.
4. As an administrator in your Confluence instance, click on the gear icon in the menu, then select Manage apps.
5. Expand the Draw.io Confluence Plugin section, paste your copied license key into the License Key field, then click Update.
   

Get a new license via the Atlassian Marketplace

If you don’t see the option to get a new trial license via your list of licenses, you can generate a new trial license via the Atlassian Marketplace.

1. Make sure you are logged into your Atlassian account and go to draw.io for Confluence on the Atlassian Marketplace.
2. Click on Try it free, make sure Server is selected, then click Start free trial.
3. Enter your organisation’s details, then click Generate License.
4. Copy the license key, and paste it into the License Key field in the Draw.io Confluence Plugin section on the Manage apps page in your Confluence administration area.