Flashing error light on all components

Hi, I’m 14 years old, and I have an old Ericsson BTS. I got it to power on, using a modified ATX power supply. The only problem is that the red error light is flashing on all of the boards. Do you know what this means, or do you know how to connect to the BTS? It has a POC card, and an ALM card. The POC card has a PROG port on it and the ALM card has a CLINK port on it. I have no other equipment so I also need to know which port is the serial port. Thank you.