my old photos are not loading. it shows unable to upload. i have tried everything regarding this. please help me fix this

Thanks for posting in the Apple Support Communities sonammbajaj,

If Photos has stopped responding while trying to upload photos, try quitting the app.

1. From the Home Screen, swipe up from the bottom of the screen and pause in the middle of the screen.
2. Swipe right or left to find the app that you want to close. 
3. Swipe up on the app's preview to close the app. 

This will allow a fresh instance of the Photos app to launch the next time you tap the icon.

You can check the status using the following steps:

1. Open the Photos app.
2. Select the Library tab, then tap All Photos.
3. Scroll to the bottom to see the status bar. 

The following page offers additional information and guidance that may be helpful: Get help with iCloud Photos

Cheers!