Some pages are showing up as 404s on the live site?

Some pages are showing up as 404s on the live site?

As the title says, my company’s site (biz2bizlinks.com) suddenly has multiple 404 errors on pages that exist and worked fine recently. As far as I know, they do not break any of the terms of use. The pages in question are:
/resources
/events
/biz-gigz 
/our-team
And maybe more that I haven’t noticed yet. Why is this happening and how can I fix it?