Thick black stripe on iMac Late 2013 after attempting to upgrade SSD

It's an iMac 21Inch, Late 2013.

Running on High Sierra.



Took it to a shop to upgrade form HDD to SSD.

They had to open the Screen in order to do that.

After setting the SSD in it's place a thick black line started showing up from the next startup.



They tried to clean the connectors. The line disappeared intermittently.

But came back eventually.



Any solutions will be highly appreciated.



Thank You

Who is the 'they'?

If an Apple Store take it straight back. If non Apple pretty dear lesson. Sure looks like LCD connections have been messed.

Not an Apple store.
We don't have any here. We do have some Apple authorized reseller though.

Could that be the connector?
Any chance of that being a software issue?

Thank You

Not likely to be a software issue but one way to check is to attach an external monitor to your 21" iMac to see if the same thing appears on the external monitor. It looks to be a hardware issue either with the connector, cables, or the display itself. Opening up a 21" iMac is always a challenge in that many things (connectors, display cables, and so forth) are easily damaged. Whoever did the work will need to open the iMac again and go over their work and make repairs if necessary.