This S2718HN was built on February 20, 2017. Shipped from Dell on December 16, 2017. The warranty expired on February 2, 2021. Run the stand alone Built-in diagnostics (page 44). If blue line shows, time to replace the monitor.
Good morning, I have a 27" Dell monitor, year around 2018. Suddenly the blue line appeared on my screen. I have tried anything but unscrew it on order to fix it. Is there something I am missing? What should I do?  Thank you in advance. Kind regards,  Bill G
S2718HN, vertical blue line