Had nerve emg of foot done for tingling and vibration, emg didn't show anything. Is that normal with sciatica? Pt isnt relieving symptoms. Next step?

EMG Has limitation. if nerve is not injured more. It will not pick up a sensory radiculopathy that still is sciatica in nature. I would at least get an MRI of the spine to verify this before evaluating other options for this pain.
Unusual. Sciatica can be due to nerve compression within lumbosacral cistern in back, but can be also peripheral such as piriformis syndrome. To diagnose electrically, need to directly examine sciatic nerve. Sciatic-like pain radiation may be seen in sacro-iliac dysfnctn. Not sure you have been diagnosed so far. Maybe an osteopath can help.
EMG doesn't show why. The problem occurred or what's causing it. It looks primarily at how muscles are reacting to a nrv problem. The problem could be in the nrv somewhere between the spine & muscle & may not necessarily be in the spine itself. Emg is helpful in determining how much nrv is being damaged & if there's a source of pressure on nrv roots. It may appear normal when nrv is damaged or "false negative".