My iPhone storage is not loading after waiting till 15 mins and even after updating to the 15.3

Try a force restart if the suggestion given by sravanKra doesn't work

Force restart an iPhone with Face ID

To force restart iPhone X, iPhone XS, iPhone XR, iPhone 11, iPhone 12, or iPhone 13, do the following:

Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the side button. When the Apple logo appears, release the button.

Wait a little longer on the same screen. Free up apps that you do not use.

No, this is not a factory reset. All your data will stay as it is.

Good luck!

This issue really annoying after ios update. no solutions are work till now.