It's probably a 5 - 10 years old version of OctoPrint.
I can't tell you why it isn't working without any logs.
Try to access it via another pc, an older mac or a vm.
It would also probably be a good idea to update the device that runs OctoPrint inside the printer.
I guess you could open it and check what's inside. Fingers crossed that it's a Raspberry Pi 2.
A computer coder spent several hours trying to install a new version of Octoprint to run the 3d printer but couldn't complete all the steps. However, an older micro memory card from 2018 was found that had the non-login security version of Octoprint on it and after using that again the printer is working great. The problem was the security add on in the newer software stopped recognizing the correct login responses which prevented any further access to the software/ printer. Unless an easy to install version of Octoprint becomes available someday for non computer expert users like myself, the old version (without the not needed security login) will remain.