I have a 5501 error on my OCE tds 400 and I will not print even when I reboot the system help

Take it back to the IT guy and ask him to fix it properly. The 'motherboard bad' was a guess which was incorrect.

It is an industrial machine and needs Canon Technical Support and Service.

https://www.google.com/search?q=OCE+TDS+400

..

I'm assuming you mean it prints blank sheets.
There could be a problem with the High Voltage Power Supply, or a short to ground in the transfer assembly.
Generally these parts are not available online. Call an authorized Oce service technician and they can get it running quickly.

System Administrator - SysAdm

The Oce TDS 600 is a large format printer made by the company Oce. Error code 23501 on this printer typically indicates an issue with the printhead. The specific cause of the error and the solution will depend on the exact circumstances of the error. Some possible causes might include a clogged printhead, a malfunctioning printhead, or a problem with the printhead cable. It is recommended to check the user manual or contact Oce technical support for more specific troubleshooting steps.

A service operator password will do you no good. The unit needs a cleaning, not a password. Call an authorized Canon/Oce technician for parts and service.

Scanner lamp not on. Shut off and restart printer and scanner. If problem persists it is either the power supply or lamp.

Check the developer and clean the charge corona and the transfer /separator corona assy.Clean the PH unit lens.

Having the software will do you no good. You need an authorized service technician to load it and configure it, and hopefully restore the old settings if there is a backup.

Sounds like a problem with an NTC. Call an authorized Oce representative for parts and service.

Replace Oce with some good product