I searched on here and saw a lot of posts but i don't see sensors on my door.

We moved in less than a year ago and have the 53515sr model. It worked fine then last week one door when trying to shut it only goes down 4 inches and then back up. I tried what other people have done on here - checked for sensor but dont see any, moved the up/down force all the way to low and nothing, moved the travel up/down screws and nothing, i see a yellow button by the wires but dont want to press it without knowing what it does

no manual from the previous owners

i held the wall opener and no difference and then i did the trick someone else had posted that when it was about to retreat i hit it again to stop it and inched it down that way and now its a couple inches off the ground but wont go up or down just to the ground and back up the couple inches

going to vacation in a couple weeks so dont want to leave it like that

also does pulling that red string just make it manual? dindt want to do that without double checking

any ideas?