1997 Mustang 4-spd auto trans won't shift into 2nd automatically

When I first start the car I put it into drive. I get up to speed and notice that the revs are climbing too high and not shifting into second. I manually shift the car from drive to 2nd and then back to drive and then the car is fixed. I am good for the rest of the trip, until I turn the car off again. What is the problem?

Is the level of the trans fluid normal?
How about the color and the smell of the fluid?
When was the last time that this transmission had the fluid and filter changed?

The problem first came up last year. I checked and changed the fluid then, without making the problem better.

The fluid level is normal.

As for the color and smell. It seems to be fine. No burnt smell at all.

Thank you