iTunes update in Mojave fails on 26.7 iPhone update attempt

When attempting to update my iPhone 15 + to 26.7, using iTunes on a MacPro (Mid 2010) running Mojave 10.14.6. Update fails! Says I need a software update before iTunes can update the iPhone but the software download never completes. Says it can’t connect to the update server?? iTunes in Mojave has always updated my iPhone 15 Plus and my iPad Pro.

Any ideas or help would be greatly appreciated!