Unable to see my friend's location on my iPhone

This would indicate an issue with your friend's iPhone. That means your friend's iPhone location was known longer than recently, but not known now due to either not being connected to the internet, powered off, or location services have been turned off. You can tell your friend to confirm the latter in Settings > Privacy and Security > Location Services > Find My > Toggle it to Never then back on to While Using the App. Return to the previous page at the top > Tap Share My Location > Make sure Share your Location is enabled.

sgreen22 ~ As your iPhone 13 Pro could be 4 years old, it's worth checking for a weak, aging battery which can cause connectivity issues — and disrupt the receipt of location information. So...

Does your iPhone 13 Pro still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health & Charging

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