Hova Bator incubator heat issue

Spring time equals .... chicks.  Just hatched 14.  Hova Bator 1602 worked fine (first time with egg turner).  Set up to put another clutch inside, but can't get the interior up to temperature.  Highest it'll go is 97 deg.  Indicator light/switch go on and off, so they're working.  "Wafer" thermostat set as high as possible.  Trying to decide which component to repair/replace.  Seems like it would be the heating element that's not putting out enough heat, rather than a problem with the wafer or the switch.  Thoughts?