[RetroGamer1985]

I would check if there are any loose contacts or parts inside the case. Carefully open the Indigo2 and inspect the graphics compartment, check if the graphic card is making contact with the riser board. If you still can't find any obvious points of failure, the next thing is get a serial nullmodem cable and go to the PROM, as suggested by mamorim01

I don’t know if the adapter only works with LCD monitors and not with CRT monitors because i i’am using a CRT monitor