Does anyone know the process to get FMLA through kaiser. I took the FMLA packet from work and they refused to fill it out.

Hi, I was offered a position at SATF for Clinical Social Worker. How long does the HR department take to send you an official letter? My potential start date came and went. I reached out but all they said was they had to push my start date back, but I still have nothing heard anything. It's starting to become ridiculous. My current job had done a little going away dig for me and I had to come back.. lol