@SteveTUK: I'm sorry to hear that you have encountered this issue with your Galaxy Z Fold3. If you press the Volume Down and Power buttons together for around 10 seconds until the phone restarts, does the issue persist? If so, please head to the Phone app, dial *#0*# into the telephone keypad, and check the Red, Green and Blue tiles. Does the line appear during any of these screen tests? If so then I recommend reaching out to our Help Desk via the link below, where an advisor will be able to arrange for the device to be inspected and repaired by an authorised Samsung engineer. Our warranty covers software and hardware defects, so any issues that fall into these categories will be repaired free of charge. If the engineer deems the fault to be the result of physical or liquid damage then a charge will be applicable, however please be assured that any costs will be communicated to you prior to the service going ahead, allowing you the chance to opt in or out of the repair.
I just had this exact issue happen to me a couple hours ago. Black line went down the center of the fold interior screen so it's dark. The left side will occasionally flicker but the image loads except for that center line. And the right side screen won't recognize touch at all.
I also had the same issue today. The screen protector started lifting in the middle of the screen after the first days of high temperature in the UK back in June. I have been unable to book a service since then despite contacting Samsung over the phone several times: same answer "book via the website". This doesn't even work. Now the inner screen is useless and none of the options apply when I try to book a repair for this issue... The Z-Fold 3 is probably my last Samsung phone. I will get rid of it as soon as I manage to get it repaired. Well done Samsung!
Yep happened to me - bought phone in December and the black line appeared in August. I decided to pay £519 to replace the screen using we fix (samsungs official repairer) and the screen lasted 6 days, im in warrenty but none of the above want to help - disgusted. Deffinately my last Samsung product and adising people not to buy