My phone says I have 494gb available (I just spent $9.99 for cloud space!) but I'm not able to take any photos!! What do I do?
I suspect you have run out of space on your phone. While you may have 494GB of space available in iCloud, your phone needs a place to put them before they can be uploaded. Try deleting some existing photos, videos, music, or apps to free up some space on your device.
iCloud storage has no correlation to a Device's available space for photos/videos/apps/etc.
To show how much space is free on the device:
Settings > General > Usage > Under 'Storage' > Manage Storage
From here you can see what is Used vs Available, and you can even see what apps are using the most.