Hi Olivia,
Gruvbox is a Palette. So in the right sidebar check the Tools - Palette button if it is set in the right way.
The attached screenshot shows an image from
tiddlywiki.com. So something may be different in you setting.
Have a closer look to the ControlPanel: Info : Advanced : Stylesheets tab
- You can drag & drop the stylesheets there .
- The last one wins. ...
- So may be you did create or import a stylesheet with a plugin ?!
- If you move the eg: plugin stylesheet up parts of the settings will be overwritten by other stylesheets in the list.
A little bit of experimentation will be needed.
hope that helps
Have fun!
mario