This is an older unit that doesn't have all those sensors. I can manually close the door and push the button to open the door but when I try to close the door it doesn't do anything.

My first guess would be to check the down force setting. If the setting is too light it won't close. Increase the force setting. You may want to also check the open limits & make sure the opener is not drawing the door open too far & getting the trolley jammed on a rail bolt.

You mention that the opener works fine on the open cycle and the door works fine manually and doesn't have photo-eyes...which leads me to believe (if the down force & limit setting doesn't help) that the logic board my be bad.

Since the opener is over 17 yrs old it may be difficult to get a new logic board. Even if you do find a logic board it may not be worth it. A logic board can easily cost $70 - 90. You can pick up a Craftsman (junkie but they do the job) for $140 - 160 from Sears. It can be hard to justify putting that type of cash into an old opener sometimes.