You may have replaced the part, but codes don't tell you a specific part is bad, they tell you a condition exists that may have multiple potential causes. Have you done troubleshooting for those causes? That thing is 22 years old with high mileage, there could be any number of issues. Was an OEM part installed?

https://www.carparts.com/blog/p0773-code-shift-solenoid-e-electrical/

https://www.obd-codes.com/p0773

Also please note for future reference that the subject line is intended for a short description of your car problem, not the full details. Thank you. (Title edited.)

If you've never changed the fluid until you started having problems, that's partly why. Automatic transmissions are designed with clean fluid in mind, not gritty fluid. 201k miles and not having changed the fluid but once for sure isn't good for that transmission. 

It also depends on how you drove the car so it got to 201k miles. Predominantly on the highway, or in the city? Driving on the highway is equal to 10% of city driving. 201k miles in the city means the transmission is worn out.