Why can't sanitize mode or hot water wash be enabled?

Kenmore Elite dishwasher Smart Wash light blinking
Sanitize Blinking Light
Some Kenmore dishwashers have a sanitize feature; when this light blinks, it means the sanitization step failed because the hot water in the dishwasher did not achieve the desired temperature or the final rinse cycle was interrupted.

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Could it be a thermostat failure?

Do you realize that to sanitize with hot water alone requires 180 degree F water? I am a hobart technician and I've never seen any business or residence with hot water anywhere near that. Residential hot water is generally approx. 120, Commercial locations generally use approx. 140, but never near 180 (tap water that hot would be a severe safety problem). Hobart LXIH machines use a built in booster heater to boost the temperature of the incoming hot water up to the required 180 deg.

Try putting the unit into a test mode. This my clear your issues otherwise call for service.

One of two ways to do this.
In standby (no lights) Press the combination of buttons:
hi temp wash > sanitize > hi temp wash > sanitize > hi temp wash
All lights will come on and the washer will run a test cycle anywhere from 5 to 10 minutes.
If that button comb doesn't work use:
heated dry > sanitize > heated dry > sanitize > heated dry

Connect it to cold water line only, never the hot line, the dishwasher has its own heating element to heat the water to the proper temperature for a clean and sanitized wash.

All Hobart dishwashers will have a wash tank heating element, but the rinse water is not heated by the dishwasher, unless it has a built-in booster heater. Usually a separate booster heater is used to heat rinse water to 180-190 deg. F for hot water sanitation.

How long between times when you use it? Any leftover water in the washer will get stagnant and smell bad if it sits for a few days

Typically "sanitation" cycles require hot water....then they add more heat to the washer during the cycle. It is not 212 degrees, but it is very hot and does kill most germs.

The mildew smell is normally caused by water remaining in the system lines - because the water drain pipe is too high and keeps too much water inside after the system pumps the interior pan. Suggest that you just pour in some bleach after the last load...that should kill all mildew. Please do not overdo it. Only about 1/8th to 1/4 cup is needed to keep the mildew smell under control

remove lower kick panel and check wire connections to heater. 2 wires go to heater terminals and a harness connector goes to temp sensor in middle of heat terminals. may be green ground connection on another term. use multimeter and check resistence on heater. during cycle heater will take time to heat.

what temp is it washing at. washing should not be the problem. This machine is designed to rinse at 180 degrees + to sanitize dishes. The machine could be converted to a chemical sanitize, it would use bleach in the rinse water instead of 180 degree water to sanitize.