Failed user login on production server using Symfony framework (Authentication request could not be processed due to...)

It looks like that the error:

Authentication request could not be processed due to a system problem.

is too generic and does not tell anything about where the problem is (there is an issue opened about this matter here).

I solved my issue by checking the logs and see what happened (in var/logs/dev.log), hoping this helps someone.

In my specific case, there was a wrong parameter in parameters.yml about database connection. But, again, the error is too generic and does not necessarily imply that the problem is related with database connection.

This problem can be fixed running command: php bin/console cache:clear --env=prod --no-debug

UPDATE: Issue solved. The issue was that a table in the entity php file was named with upper case letters while the database table was named with lower case. +1 to ClémentBERTILLON for pointing in the right direction, namely prod.log