"The cassette fan is off" and "The lamp is off" are messages given when the detector does not see any light during instrument initialization.
The "burn" mark on the lamp is normal for a used lamp and the lamp should still function properly. It is caused by sputtering of material inside of the lamp. The spot can interfere with the light output level if it is in the light path to the detector, but would not cause the messages above.
The cause of no light detected can be due to different reasons. The recommended procedure for testing the lamp is to remove the capillary and run the lamp output test. Some causes of the light not being detected:
A bad lamp (not turning on)
The cassette not being installed
A missing interface
A misaligned interface
Broken filter assembly (there should be a loud noise when the filter assembly is moving that is heard when the instrument is switched on)
I suggest running the lamp output test and checking the cassette and interface installation. You could also replace the lamp and see if the messages stop. Hope this helps.