Is it because the battery has been changed?

If you had it changed at a non-Apple authorised repair shop, then they didn't replace it with a genuine iPhone battery and it's not going to perform like a genuine iPhone battery.

Yes, you will have issues with it such as not displaying the battery health.

sorayal210 Said:

"Is it because the battery has been changed?: I can’t view my battery health"

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Revealing the Battery Health:

Report back what happens when you perform the following...

1. Go To: Settings
2. Tap: Battery
3. Tap: Battery Health
4. View: Percentage

Time for a New Battery?

When the Battery Health is 80% or lower, it is time for a new battery.