1) Make sure the HPD signal is high on the output connector. Usually the monitor sets the signal high indicating it's connected. Then run the script
2) Make sure the TMDS lines are about 3V, this means the 7513 sees the correct load on the TMDS lines. Use scope or DVM
The transmitter will normally power down if HPD goes low or Monitor sense goes low. The uP will monitor these bits in the part and resend the script when they both go high to power up the transmitter.
Also with a scope you should be able to see 65MHz on the TMDS clock line, hard to see but it's there if you good with scope probes.
You need to begin testing with DVI sources and DVI sinks with no HDCP. Your FPGA is a good DVI source and use a PC monitor. You don't want to have issues with HDCP since is just make life harder.