Before uninstalling Refined for Confluence, revert Confluence back to its default theme. This prevents issues that may occur when Confluence looks for a theme that doesn’t exist anymore.
Head to Confluence Administration.
In the left-hand menu, scroll down to the Look and feel heading and click Themes.
Under Choose new theme, click Default theme.
Then, to uninstall Refined:
In the left-hand menu, scroll down to the Atlassian marketplace heading and click Manage apps.
Click Refined for Confluence > Uninstall.