no ethernet cable connected? R6250

> [...] My router randomly stopped working [...]

   "stopped working" is not a very detailed description of anything.

> [...] it's now saying there's no Ethernet cable connected to the
> internet port when there is. [...]

   How, exactly, is it "saying" this?  Is it speaking to you, or are you
looking at a web page, or are you looking at an LED indicator, or what?

   How have you verified that this cable is good?  Does the
(unspecified) device at the other end of the cable "say" anything about
it?

> [...] I am frustrated [...]

   Reading a problem description like that, so am I.

> [...] and do not know what to do. [...]

   For a start, you might try reporting your actual actions and
observations, rather than vague descriptions or interpretations.

   You might also visit http://netgear.com/support , put in your model
number, and look for Documentation.  Get the User Manual.  Read.