Viking vgsc306 range oven replaced igniter,oven will not stay on. What else wrong.

The igniter just lights a pilot and then a flame rod proves the flame. Probably the only problem was that the flame rod was dirty. It looks like a platinum spark plug and extends into the flame. If it's dirty it will not conduct electricity and prove the flame is on. Clean it with some 3000 grit sand paper and all will be well. Your igniter was most likely good. They do not usually go out very often. In 35 years I have only had one bad. Dirt is the cause almost every time.