transmission won't engage 1st gear

Is this determined by second gear starts, otherwise considered a lack of power from a stop? With the miles on the vehicle, how has the maintenance been on the transmission? What condition is the transmission fluid in?

Changes fluid and filter to try to fix it but didn't work, hardly debris in pan on magnet. installed new filter and fluid. Same problem continues won't engage in first gear.

So to be more specific, would you say it has second gear starts? Have you determined that it has second, third, and fourth gears? Based on what the symptoms are, it is going to be most likely, an internal transmission concern. A faulty solenoid is going to give you a concern with another gear, in addition to no first gear.