Assuming you have made no changes, as reported on the forum over the years, replacing the ethernet cable will fix the issue 9 out of 10 times. Sometimes, jiggling it will cause it to respond for a while (days, hours, sporadically - which was what was happening to me). I finally bit the bullet and replaced the ethernet cable - no issues from that point on - about a year ago. Unfortunately, they don't give away ethernet cables; they are expensive for what little there are to them.
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