How do I repair a drywall tape crack on my living room wall?

sand it down and retape.

Here is a great tutorial on how to do it. Be sure to lightly sand between compound coats.

https://www.dummies.com/home-garden/walls-ceilings/how-to-fix-large-cracks-in-drywall/#slide-1

Scrape off the area that is "bad". You might have to do some light sanding as well. Smooth the area as much as possible. Tape over the cleaned areas.

Spread sheet rock mud over the tape and any other places where you need smoothed or repaired. Let dry. Take a damp sponge and smooth out rather than sanding.

Repeat the mud, dry, and smooth process until it is completely unable to notice. Usually three times.

Now you are ready to paint.

For myself, I would use a utility knife/box knife to cut the old drywall tape for about an inch beyond the damage. Clean away any loose crumbly material.

Now, you have a choice of drywall tapes. Paper or selfstick mesh. My choice in this case is the selfstick variety. Make sure that it doesn’t extend beyond the edges of the peeled area even if you need to trim it a little. When your tape is stuck down good, take a wide spreader, at least 4 inches across and lay a good not gloppy layer of drywall compound over it and let dry overnight. The next day just sand it smooth and you’Re ready to paint.

bingoi

PEEL off the old tape. Use a scouring pad for dishes to scrape down the edges & remove the dust & paint where it came off. Retape & use sheetrock puddy to cover the tape. Make sure to blend it in with the existing paint around the tape's edges & make it smooth. Repaint. That's it. Hope this helps. :)

Use a Filler from DIY store and rub down when dry!