You may be experiencing any of these issues:
The newly enhanced Themes app has been integrated into Personalization settings, enabling you to customize all aspects of your phone. In addition to being integrated with the settings, the new Themes functionality enables a new Freeform layout enabling you to create custom icons that can be placed anywhere on the screen without being snapped to a grid. Customizable options include:
Themes are applied to the lock screen, home, Blinkfeed, dialer, and all apps for a unified experience across the entire phone. You can also create custom themes on their computer using the HTC Theme Maker at https://themes.htc.com and download them to your phone via the Themes app.
HTC Theme Maker allows for more customization options, as well as the ability to publish custom themes for other users to download and rate. Some Themes icons have different icon imagery than the standard icon set. Please keep this in mind when following troubleshooting steps that use icon descriptions.
Downloaded font/sounds/icon packs may not appear when creating a new theme. Follow these steps to use downloaded components in a theme:
Follow these steps to edit the current phone theme:
To order to move icons and apps off the home screen grid, you must be using a Freestyle home screen layout theme. Follow these steps to see if the current theme is a Freestyle Layout.
If theme colors are hard to see or desired color is not available, you can scroll to a different style for a different selection of color options. If the desired colors are unable to be selected in the Themes app, full color customization is available at https://themes.htc.com. You can create themes with specific colors on the website using the Maker Pro tools, and then download the created theme once finished.
Some theme content will remain even after the theme has been deleted.
NOTE: If the active theme is removed from Themes, the phone will retain the wallpaper, icon, font, and sound settings from the theme until it is replaced by a new theme or by manually changing the settings.