App Dark Mode
If you are unable to set your Custom Timer in the Time Timer App, it could be that you are using Dark Mode on your device. This will effect certain features within the App such as setting the Hours, Minutes and Seconds and well as darkening the color of the Header and text. Please take your device OFF Dark Mode while using the App.
If your phone needs to remain in Dark Mode, please create your Custom Timers in Light Mode first and make sure to SAVE them before you switch your device back to Dark Mode.