I had to use Microsoft Edge to connect to Paperbackswap. My browser of choice, Chrome, can't connect. It says 

504 Gateway Time-out

The server didn't respond in time. PBS Team

 i'm using chrome and everything seems fine on this end.

i am also on chrome and all is okay

when you get that gateway timeout just wait a moment and try again. Or you might restart your computer and then try again.

Or close your browser, then reopen it. I had the same problem recently in Firefox.

I’m experiencing the same problem now on Safari. 

Using Chrome on my PC with no problems.

Just checked safari on my iPad & iPhone no problems either.

Actually, there are times I think the server for PBS doesn't have enough band-width or RAM to handle to many hits. Then, when the load gets too heavy on the server, it times out on your browser.

Just had the same problem with Safari, but tried again and got right on.

It ended up working again.

I am unable to get to CMT and CA&P with Google Chrome.  I can get to the other forums on this site, just not those 2.  Any idea why?

I was able to access most of PBS (other than CMT) on Google Chrome, now I can't even get on PBS with GC.

My educated guess on this is that they are doing maintenance or backup on some of the components that run the system, and so portions are unavailable or limited in what they can handle.  If true, this would be another example where if they know ahead of time they could have a post specifically warning us, instead of having to answer these questions all the time & speculating.