Lightroom 5 Error: The following files were not imported because they could not be read. You know the annoying bug?
The following files were not imported because they could not be read.

Adobe has never really fixed the bug, although it has not yet answered in the Adobe forum.
First of all: No, you didn't do anything wrong!

The day before yesterday I imported about 50 new pictures (JPG) from my iPhone and today (same iPhone, same iOS and identical Lightroom version 5.7.1: Suddenly LR can't read the JPGs anymore.
I know the same error with my Canon RAWs.
Change card, change reader, install camera update: Nothing helped. The error simply went away by itself.

The background seems to be write or read permissions of the source files or destination folders.

Here's a workaround on how to still get the images into Lightroom and work with them.

You copy all the pictures manually from the memory card or smartphone to a folder on your hard drive.
Then you automatically import these images from this folder and that's how it works:

Lightroom Menu: File > Automatically import > Automatic import settings
First you choose a "Monitored folder" that is the source folder to which you copied the images.

Then you name/select a destination folder (ideally where you put the pictures otherwise)
Please create this folder as well.
I am using a folder with today's date: 2018-09-20

In the same settings window, click on the checkbox "Activate automatic import" at the top.
As if by magic, all images from the source folder are moved to the destination folder and the images are imported into Lightroom.

I hope this works for you too!