Comcast Internet went out, Comcast restored service but my account is still inactive. Waukegan Nationwide

I'm not really perplexed why their Tech Support went right to the "bad modem",  sadly most cable companies first level support are generally nothing more than reading off a script.  If you try to engage them in conversations that vary from what they are "allowed" to say...you will find they will not answer it.    Usually if the first level doesn't help, you need to push to get a higher level support person...sometimes they will sometimes they won't.

But what confuses me is you say it appears that your WiFi is running, it is just your computer(hardwired) is not.  If this is the case it may just be a simple case of rebooting things in order. 

First unplug your Cable Modem, if there is a battery backup in it..remove it.  Unplug any other routers you may have.  Shutdown any computers that may be on. 

Give it at least 45 seconds before  you plug your Cable Router back in.  This will give it time to clear it's memory and basically forces a reset.  Once the modem comes up, plug your router back in and let that boot.  Once that is up...go ahead and turn back on your computers.  That SHOULD reset everything and allow your computer to see the modem.  Now, if it doesn't you may have other issues.  That running various things on your computer could force a reset..such as checking the network settings such as your DNS and gateway settings to make sure that they are still correct.

Including the possible coincidence that your modem just happen to die at the same time.

Now, the question is are you renting or did you buy the modem?  If you are renting it, they should allow you to just swap it out by going to one of their centers. 

Again, I am just mentioning this if you didn't try it already.  If you have you may want to call back and see if you can get a higher level support, or even have them make a visit to make sure there isn't someting wrong in the cables.