OK. I figured it out. This could help some people who have recently started using Cloudflare CDN from Bluehost. Cloudflare recommended that I change my URL from domain.com to http://www.domain.com.
Clicking on my “Submit an Event” menu button would take the user to a login/register page, and then would redirect back to the home page afterwards. What I noticed is that page had the address domain.com/event-submission instead of http://www.domain.com/event-submission. Therefore it was pointing to a cached page, and not the current page.
I went to Appearance > Menus and changed the reference from domain.com to http://www.domain.com and it fixed it. Then, I went to myPHPAdmin and did a search for other references and changed them too.