Sorry, This page doesn't seem to exist

I’m working with a web designer to redo my website. It is on a subdomain until we get it all pretty. ( incase that matters with this problem. ) We have done a lot to the site, but two pages keep coming up with the error “sorry, that page doesn’t seem to exist.”

Please note: I know enough to be dangerous. My old site was in html, and I did it and it is very, old so, if you explain things please explain them in simple terms. I have forgotten a lot about this web design stuff. I’m a sculptor not a website back end person. The website sub domain listing is https://wordpress.creativesculpture.com/
The two pages that I have this problem with is "workshops and lectures "and “published works” under the “author” menu. We have successfully gotten the rest designed, though I’m still adding content, but these two pages keep coming up with this error. Server guys say if they don’t use BB they can make them but BB keeps coming up with this error. upper level person at hostgator said someone else had this problem two weeks back.

Server guys asked me to ask you about “settings,” “updates” and “other steps” to take care of this. Again, please tell me what to do and HOW to do it. Thanks.