CSU power cycle failure

Symptom
After a CSU fatal error, CSU was power cycled and it would not complete a CSU start operation (modify -s mcsus csustart=1).
Problem
The CSU connection failed.
Diagnostic
Have the night attendant or an engineer at the summit checking the MOSFIRE CSU Rack Control (MOSFIRE rotation angle 180 deg) and checking that all switches and lights look like the following picture:

Solution
Have an engineer with the appropiate skills clean the fibers. That fixed the problem as explained in daylog ticket K1-26240