We have some old servers, switches that want to replace. Have posted in Offer section already, but wonder if there is any other place we can sell? I tried eBay before, but it seems not successful
Thank you.

You can search to other webmaster of webhosting related websites with a second hand advertisement place??

Craigslist may not be a bad idea. Not quite the reach of eBay, but it's free to try.

Here, and eBay would be your best bets.
If its not successful, try revising your prices.
I sold a 2 week old cash register on ebay for more than i bought it for, and i started the auction out at $25, I bought it for $200, it sold for $285.
Wording, pictures, etc are the things needed.

I've had crazy success with Craigslist. No matter where you list it, include good photos and be as thorough as possible with the description and/or technical specs. The better the quality of your listing the more likely you'll sell. I'm constantly amazed at the older hardware I've been able to sell.

You could even try contacting some data centers like FDC Servers etc.

Craigslist now asks me for phone authentication for posting. I am not in the US, so, it's out of options. I will try eBay again :)
Thank you.

Maybe some of the craigslist clones like backpage.com or kajiji.com?

Drop them to the trash where it belongs.

I've sold a ton of hardware on craigslist too.