To address the issue of CuriosityStream only playing the first two minutes of videos, follow these detailed steps:

1. Check Subscription Status: Confirm that you have an active subscription. If you are using a free trial or have not subscribed, you may be limited to preview lengths. Ensure your membership is valid by checking your account settings on CuriosityStream.

2. Clear Browser Cache: If you are streaming from a web browser, clearing your cache can resolve playback issues:
- For Safari: Go to Settings > Safari > Clear History and Website Data.
- For Chrome: Open the browser, click on the three dots in the upper-right corner, select More tools > Clear browsing data.

3. Disable Ad Blockers: Some ad blockers can interfere with video playback. Temporarily disable any ad blockers or popup blockers and try playing the video again.

4. Update Your Browser: Make sure that your web browser is up-to-date, as using an outdated version can lead to compatibility issues. Visit your browser's official website for instructions on how to update.

5. Try a Different Browser: If the problem persists, try using a different web browser. For instance, if you are using Safari, switch to Chrome or Firefox to see if the issue is resolved.

6. Check Internet Connection: Ensure you have a stable internet connection. Streaming services require a strong connection; consider running a speed test to verify your bandwidth.

7. Restart Your Device: Sometimes, a simple restart can fix playback issues. Turn off your device and power it back on.

8. Check for App Updates: If you are using the CuriosityStream app, ensure it is updated to the latest version. Go to the App Store, search for CuriosityStream, and update if necessary.

9. Contact Support: If none of the above steps resolve the issue, reach out to CuriosityStream support. Visit their help center for troubleshooting tips and to submit a support request if needed - learn more.

By following these steps, you should be able to resolve the problem and enjoy full-length documentaries on CuriosityStream. If issues persist, consider exploring discussions around the issue on forums such as Reddit, where users share similar experiences and solutions - learn more.