Struggling to set up new iPhone, keeps on asking me for Apple ID password
I got myself a new iPhone SE second generation... I cleared most of the photos from my old iPhone, and stored them on separate hard drives and on my iMac in a separate folder. I then back up the old iPhone SE, then I set up the new iPhone in the process of moving to a new Phone.. It does most of the things right, but where the problem happens, is it keeps on asking me for my Apple ID password in a loop. I removed the sim, put it back in the old iPhone because of this problem, which means I still need to use the old iPhone until this is sorted. I suppose I thought I needed to change my password... and that is what I did.. which was tedious, which means I have to relog into my iMac, Mabook Pro, iPad , old iPhone... and new iPhone.. my existing devices were fine.. but the new iPhone still throwing up the pop up dialogue, asking for the password after it it has been entered in several times, I want to scream. I am now reformatting the iPhone with Restore in iTunes, and probably try start over again, this time via iTunes, restoring from the backup from my old iPhone... don't know if that work... I hope this isn't a hardware issue, with the new iPhone.
I am wondering is it because I need to update the old iPhone to match that of the new one ?
(I have managed to make an online Personal Session now ) which might be of help... but it is only on Thursday..
iPhone SE