DIAGNOSIS Yes, this is normal operation for this model. The visual window is more for checking food color at the end of a cycle, not for monitoring during cooking. Steam and condensation from the food obscure it.
FIX There's no fix to prevent fogging during operation. Rely on the timer and internal temperature, not sight. To briefly check progress, pull the basket out (cooking pauses). The window will clear in a few seconds once the hot, moist air escapes.
IF THAT DIDN'T WORK If the window is permanently cloudy or has a white, etched film even when cold, it's likely coated with polymerized grease. Clean it with a paste of baking soda and water, not abrasive scrubbers that will scratch the plastic.
HEADS UP Never spray glass cleaner or other chemicals directly onto a hot or warm window; the thermal shock can crack it. Always clean when the unit is completely cool.