Mike, do you have a hand-held programming console? What program is installed? To determine the program, look at the PLC of the machine. Near the bottom, you should see a cover that you can remove where the EEPROM chip is installed. For an OHD, the first 5 digits of the program number will be either 23953 or 26234. The program will help me to identify which version of OHD you are running.
If you can't find the program number, if you can provide the serial number, that will help me to know exactly what you have as well to assist.
If you can drive the gantry forward and reverse on the tracks, and you can drive the trolley left and right, this indicates the forward/reverse direction relays should be working properly. It should be able to rotate forward and reverse as well if the other movements are working.
If you have a hand-held programming console and know how to use it, there are two data registers that you need to look at. M8044 will turn on if all the proximity switches are in their correct state when the machine is supposed to be at home. M141 looks at the state of M8044 and a few other items such as VFD fault signals, reclaim faults and others that can cause a "not at home" code. Most likely, you will find M8044 is not on due to a prox being in the wrong state. If you don't have an HPP, we'll need to look at inputs to determine what is going on.