ERROR: function sha256(bytea) does not exist

In case that you are trying to upgrade the version on your IriusRisk, and the startup fails with the following error in the logs:

iquibase.exception.DatabaseException: ERROR: function sha256(bytea) does not exist

Please, review that you are using a compatible version of PostgreSQL, as commented in the Installation article.

As you can see in this documentation, the SHA256 was introduced in PostgreSQL 11. 

Upgrading your PostgreSQL to a compatible version will solve the issue.