Hello JamesJ502,
If you're not receiving alerts for your notifications, you'll want to make sure you have an alert set up for whatever application it is.
Use notifications on your iPhone or iPad
Make sure the device is in ring mode. Check the Ring/Silent switch above the volume buttons to make sure it is pushed towards the front of the device with no orange showing.
How to put your iPhone on vibrate, ring, or silent mode
Make sure you do not have Do Not Disturb or Focus enabled on the device. Go to Settings > Focus and see if anything is turned on. If something is turned on in there, turn it off.
Use Do Not Disturb with Focus on your iPhone or iPad
Cheers!