In the Lightroom app on my iPhone,I can ‘t delete any imported photos,Even after uninstalling and reinstalling the app,the problem still remains.

Please update to the LR iOS app v11.3.3 that is now available on the iOS App Store.  Visit the app listing, and you should see the update become available.

Please explain in more detail. How do you try to delete a photo? What does (not) happen when you try it?