Check settings and record symptoms
Confirm Heat mode and a temperature setting above the room temperature. Note the display, timing, noises, and any visible fault code. Check that accessible grilles are unobstructed.
Leave internal testing to a professional
Keep panels closed, leave gas and electrical parts alone, and avoid repeated resets. If the furnace remains off or unreliable, contact a qualified contractor.
Take this question into the conversation
“What did you find, what will the proposed work solve, and how will we know it worked?”
This is general educational guidance, not an assessment of your equipment. A qualified contractor must evaluate the actual system.