https://johnlinhart.com/blog/uh-oh-mautic-upgrade-was-not-successful
1. Try to clear cache
When the upgrade failed in the last step, it's possible that only the cache is outdated. Try to clear it manually.
php app/console cache:clear
If this command throws a PHP error, you can try to nuke the cache folder like this:
rm -rf app/cache/*
If clearing cache didn't help, continue with next step.
2. Trigger update manually
Firstly, let's find out if there is some version to update to.
php app/console mautic:update:find
Output of this command should tell you clearly if there is a new version waiting to update to. If so, run:
php app/console mautic:update:apply
If there is no update to run, try next step.
3. Try to run database migrations
Let's check if there are any migrations to run.
php app/console doctrine:migration:status
If there are any, be sure you have backup of your database and then run:
php app/console doctrine:migration:migrate
4. Try to update database schema
If the upgrade failed in the step of database update, this could solve it. Let's check if the database schema is up to date.
php app/console doctrine:schema:update --dump-sql
This command outputs if the database schema is up to date with the code. If there are some queries to execute, backup the database! if you haven't already and run:
php app/console doctrine:schema:update --force
If that didn't help, try the next step.