Here is a problem I have come across twice now. Every time you migrate Apple computers it will corrupt a file so that Netflix will no longer work. So for me I migrated from a Macbook pro to a Mac Mini then back to a Macbook Pro over a series of 3 years. It seems like this is an on going issue so here is the simple fix.
The file that gets corrupted is the mspr.hds file, you can find it here.
HD > Library > Application Support > Microsoft > PlayReady > mspr.hds
Simply delete it and you are good to go. A lot of sites seems to recommend you keep the old mspr.hds by renaming it something like mspr.hds.old then just refreshing your browser that you watch Netflix in. I don’t really see a reason for that, you can always reinstall Microsoft Silverlight.
For me the fix worked instantly, comment below if you need more help. Remember that Netflix’s help line is actually really easy to reach and will help you out.