I was simply updating from 5.3 to 5.3.1 and got the following error on System Status Page -

Sorry, due to an error, we are unable to fulfill your request at the moment. You may want to contact your administrator or service provider with more details about what action you were performing when this occurred. You have requested a non-existent service "civi_flexmailer_required_tokens".

This error replaces the entire System Status page. I resolved it somehow by disabling flexmailer and mosaico and then re-enabling them. Quite odd.

Update: This error also occurred when updating from 5.3.1 to 5.6

  • 1
    When posting questions, you can choose to answer them yourself, which makes it easier for folks to find answered questions. Commented Jul 24, 2018 at 23:26

1 Answer 1


I resolved it by disabling Mosaico, then Flexmailer; and then re-enabling them in the opposite order: Flexmailer then Mosaico (the order is important!).

I used the Administration screen to manage CiviCRM extensions; but you could also use Drush if your Civi is on Drupal.

  • Can you accept your own answer? Fixed the issue for me as well. Commented Sep 29, 2018 at 7:32
  • The order is important! Flexmailer is a dependency of Mosaico so you have to disable Mosaico first then Flexmailer. To re-enable them, it's Flexmailer first then Mosaico. Commented Feb 20, 2020 at 15:54

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