First time my daughter developed plantar, doctor had her stop all running for two weeks and then slowly ease back into running. 2nd time her plantar problem returned is when I was able to massage out problem and she was running next day. Massaged her foot for two more days and she was pain free. First massage is where you really get deep into tissue and it does hurt.
With my daughter we noticed she had worn shoes with no arch support the day before foot started to hurt. Now we make sure all her shoes have good support, not always easy to do. She felt problem coming on at beginning of XC. I easily found the knot and massaged it out and she was running next day with no problems. However, I think we fixed it before it got bad.
First time I developed plantar, same thing, two to three weeks no running. Second time it started with feet becoming very sore after running. I went straight to the treadmill and was able to keep running, about two more weeks. I got about 5 min into my run and then pain was too much to continue. Massaged my own foot and was back running the next day. Foot was definitely sore at the start, but it loosened up and I was able to continue running pain free after that day. I massaged foot thoroughly for the next week. Now I know what to look for ( how it starts) and I massage right away.
I know how painful plantar is and it gets to where there is no way you can continue to run on it. This worked for me and my daughter. Hope you get better.