Naps in crib ... HELPPPP

Ok, so I posted a few days ago that I got my 4 month old to nap in her crib for the first time! I was so excited and happy danced for 3 days because she did it 2 days after that too (only for 35 min at a time, but hey, it was something). Day 4 and no, she’s not having it or day 5 or 6. We both end up crying. I don’t know what else to do. I’m at stay at home mom and a work from home mom so I need to be able to put her down for naps. For the 3 days it worked, we turned on the sound machine, swaddled, and read a book. I put her down and let her fuss for about 15 min and she would fall asleep. My ped said I could go up to 20 min, but she never did that until day 4. Now if we get near the crib she screams! She will not let me put her down. What else can I do?!