If you are getting this error, don't worry. It's not on your end. Sony are undergoing maintenance on their services and it's knocked out access to PS+.
I'm not sure how long this will last as their maintenance was supposed to start Monday. If this is the planned maintenance started early then it will be down for several hours.
If you have a PS3 then use that for the time being as it's free online. If not then you will need to sit tight.
Hope this helps.
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