Hi, My Mother Age 72 Has Stage III Ovarian Cancer,

Hi, my mother age 72 has stage III ovarian cancer, had surgery to remove or debulk, taking one ovary, two pieces out of intestine and scraping of the abdominal lining.... After long recovery (21 days) then in nursing home for rehab, had a setback with acute renal failure, back in hospital, now not been eating (malnutritioned) they inserted a PEG tube yesterday, started feeding thru tube this morning, as of this evening she is not digesting anything, my question is WHY would this be happening???? Still waiting on doctors to respond to nurse call... Thanks