This can be caused by different issues. Usually, it’s due a misconfiguration, these below are some tips that may help you to resolve it.
1) WordPress Permalink Structure Settings:
2) Users Ultra Permalink Structure Settings:
Go to WordPress Settings – Permalink.
For example: if you profile’s URL looks like http://yourdomain.com/profile/user-name, then the profile slug should be set to “profile”, if you use a different slug for your profile’s URL please make sure to set the same slug in the “slug” box.
3) Very Important:
In this example we’ve created the page “View Profile” which has the slug “profile”.
We have to set the same page we’ve just created in the Permalink tab. Make sure you’re using the same slug. If you used the slug “member-profile” then make sure that the page has that slug as well. They should match, otherwise you will get a 404 error.