To address the issue of being unable to download videos using Instant Save on your iPhone, follow these detailed troubleshooting steps:

1. Check App Permissions: Ensure that Instant Save has the necessary permissions to access your photos. Go to your iPhone's Settings, scroll down to Instant Save, and check if you've granted permission to access your Camera Roll.

2. Reboot Your Device: Sometimes, simply restarting your device can resolve connectivity and app performance issues. Hold down the power button and slide to power off. Then, turn your iPhone back on.

3. Update the App: Make sure you are using the latest version of Instant Save. Open the App Store, search for Instant Save, and check for any available updates. Install if necessary.

4. Check Internet Connection: Confirm that your internet connection is stable. Switch between Wi-Fi and cellular data to see if the issue persists.

5. Clear Cache and Data: If possible, try clearing the app's cache. This is typically done by uninstalling and reinstalling the app. To do this:

- Long press on the Instant Save app icon until options appear.
- Select Remove App, then confirm by tapping Delete App.
- Go back to the App Store and reinstall Instant Save.

6. Try Different Video Links: Sometimes, there may be issues with specific video links. Try pasting different video URLs to see if the problem is isolated to certain videos.

7. Use Alternative Methods:
- If the app continues to disconnect, consider alternative ways to save videos, such as using screen recording on your iPhone.
- Go to Settings > Control Center > Customize Controls, and add Screen Recording.
- Swipe down from the upper-right corner of your screen and tap the screen recording button. Start playing the video, and it will record your screen and capture the video.

8. Report the Issue: If none of these solutions work, consider reaching out to Instant Save support or look for user discussions on platforms like Reddit, where users share similar issues and their solutions. For instance, there might be specific bugs or server issues affecting the app's functionality – learn more - learn more.

By following these steps, you should be able to troubleshoot the problem and successfully download videos using Instant Save.