That sounds frustrating. A single vertical line on the screen of your Loading... typically indicates an issue with the display hardware.

Before we dive into a full repair, let's narrow down the cause with a couple of questions and an initial troubleshooting step:

1. When did the blue line appear? Did it happen suddenly, after a drop, or after a recent screen replacement or repair?
2. Is the line present at all times? Does it appear during the boot-up sequence (when you see the Apple logo)?

Immediate Troubleshooting

The first thing to try is a Force Restart, as this can sometimes resolve temporary software or display driver glitches:

1. Press and quickly release the Volume Up button.
2. Press and quickly release the Volume Down button.
3. Press and hold the Side/Power button until the screen goes dark and the Apple logo reappears.

If the line remains after the phone restarts, the problem is almost certainly hardware-related—either a loose connection or a faulty display panel.

Hardware Diagnosis

If the line is still there, here is the technical breakdown:

• If the phone has been opened recently (e.g., for a screen or battery replacement), the most likely cause is a loose display connector on the logic board. The resources I have show that this is a very common issue after a DIY repair. The fix is to open the phone, disconnect, clean, and securely reseat the display's ribbon cables. You can find detailed steps on how to do this in the Loading....
• If the phone has NOT been opened recently and the line appeared spontaneously or after a drop, it likely means the display assembly itself is damaged. The liquid crystal display (LCD) panel is cracked internally, which is causing that specific column of pixels to fail as a solid blue line.

If you suspect the screen is faulty, the solution is to replace the display assembly. You can find the part here: Loading....

Let me know if the force restart helped, and if the line appeared after a recent repair. This will tell us whether we need to reseat a cable or replace the screen.

It sounds like a screen replacement is the most likely solution if the line persisted after the force restart. A vertical line typically indicates a failure in the internal connections of the display panel.

The good news is that replacing the screen on the Loading... is a very common repair.

Here is the step-by-step guide you'll need for the procedure:

Parts and Tools

To complete the repair, you will need a few specialized tools and the replacement screen:

• Replacement Screen: You will need a new Loading....
• Tools: The process requires removing pentalobe screws, tri-point screws, and standoff screws, as well as lifting and separating the display. The essential tools include:
  • P2 Pentalobe Screwdriver
  • Tri-Point Y000 Screwdriver
  • Standoff Screwdriver (for the connector shield)
  • iOpener or Heat Gun (to loosen adhesive)
  • Suction Handle and Opening Picks (to separate the display)

A comprehensive kit, like the Loading..., contains all the necessary drivers and opening tools.

Important Note on Apple's Software

Be aware that after replacing the screen, you will receive a non-genuine display warning in your settings. This is a common consequence of replacing the display on modern iPhones, as Apple's software is designed to detect non-OEM parts. This warning does not affect the functionality of the new screen or the phone.

Let me know if you have any questions before you start, or if you'd like a quick overview of the most critical steps in the repair.