If the Curious app is not opening in workout mode, here are the most relevant troubleshooting steps based on available sources and best practices for similar app or mod issues:

1. Check for Known Compatibility Issues
- If you’re referring to the Curios mod (often used in Minecraft for managing equipment slots), a common cause for the GUI not opening is a conflict with other mods or plugins. For example, users reported that uninstalling the SkinsRestorer plugin or mod fixed the issue2. Make sure to check for any plugin or mod recently added or updated that could be causing a conflict.

2. Ensure Slots Are Registered (for Curios mod)
- The Curios GUI will not open if there are no slots registered. Check the mod’s settings or your configuration to ensure appropriate slots are available. If there are none, the GUI has nothing to show2.

3. Basic Troubleshooting Steps (General Apps)
If you are using the Curiosity app for productivity or search, and it’s failing to open:
- Restart your device to resolve temporary glitches6.
- Uninstall and reinstall the app. For Windows or Mac, use the standard uninstallation method, then download the latest version from the official website36.
- Clear app data or cache. On Windows, you can locate Curiosity’s data folder and delete it by going to %appdata%/curiosity/localstorage3.
- Check for antivirus blocks. Sometimes, antivirus programs can prevent Curiosity from running, causing it to crash or preventing it from opening. Temporarily disable your antivirus to test if this resolves the issue3.
- Update your operating system and the app to the most recent versions6.

4. Platform-Specific Issues (Apple Silicon/Mac)
- If you’re on a Mac with an Apple Silicon chip (M1/M2), download the special Apple Silicon version of the app. There is a known issue on these devices where the app won't open or quits unexpectedly unless this version is used3.

5. For Fitness-Related Apps and Devices
- General troubleshooting: Restart the device, check for updates, and reinstall the app if necessary. If the workout mode specifically won’t start, double-check device compatibility and permissions—especially permissions related to health data or sensors6.
- If using a smartwatch, unpair and re-pair the device to reset connections (as with Apple Watch troubleshooting)1.

Summary Table: Troubleshooting Steps

| Issue Type | Possible Fixes |
|-------------------|---------------------------------------------------------------------------------------------------|
| Mod/App conflict | Remove conflicting mods (e.g., SkinsRestorer), check for registered slots (for Curios mod)2 |
| General crash | Restart device, uninstall/reinstall app, clear cache/data folders, check antivirus36 |
| Mac-specific bug | Download correct Apple Silicon version (for Curiosity app)3 |
| Wearable/device | Unpair and re-pair, recalibrate sensors, check for updates1 |

If you specify which "Curious" app you are using and your device/platform, more targeted troubleshooting can be provided. If these steps do not resolve your issue, please describe any error messages or additional symptoms you are experiencing.