Users should be able to manage their own MFA settings by using the same URL they accessed to set it up initially: https://aka.ms/MFASetup
If users are having issues with accessing Office 365 resources via MFA and cannot resolve their issue on their own, we can reset their MFA settings for them so they can run through the setup process from scratch again.
1. Go to the following URL and sign in with your CCM email address and password: https://portal.azure.com/#blade/Microsoft_AAD_IAM/UsersManagementMenuBlade/AllUsers
2. You will see the following screen: 
3. Use the Search field to find the user that is having an issue:
4. Clicking on the Name of the user takes you to the following screen:
5. Here you will want to click on the Authentication methods link on the left side of the page.
6. Doing so will take you to the following screen where you will want to click on the Require re-register MFA link in the middle of the page:
7. The user should now be able to go to the MFA setup link and run through the configuration process again.