Why can't I update core from 8.6.16 to 8.7.1? I need to update my Drupal 8 site from 8.6.16 to 8.7.1, but when I run composer update drupal/core --with-dependencies it says "Nothing to install or update". I have been banging my head on the wall about this for 45 minutes, and haven't found anything on Google that fixes this. 

Does anyone know why it says there is an update, but then says there is nothing to update or install?
There seem to be some version dependency issue with that email-validator. 

I solved it by updating the composer.json to the newer version before updating Drupal: 

composer require drupal/core:~8.7.0 --no-update
composer require webflo/drupal-core-require-dev:~8.7.0 --no-update
composer update drupal/core webflo/drupal-core-require-dev --with-dependencies --dry-run
composer update drupal/core webflo/drupal-core-require-dev --with-dependencies 
cd web
[../vendor/bin/]drush updatedb
[../vendor/bin/]drush cr


YMMV, here is the Issues where you can get more help if this doesn't work (check the related Issues as well): 

Cannot update to Drupal 8.7.0 from 8.6.15 -- egulias/email-validator version conflict  

Don't forget to attach your composer.json and composer.lock there so the problem can be properly diagnosed.