Hi Pablo,

mod_exercise does not exist in the 2.2 Totara core code. When upgrading from 1.1 to 2.2 you need to make sure you backup then remove ALL the 1.1 code first, as the two codebases are completely incompatible. Extracting a zip of the 2.2 code over the top of the existing 1.1 codebase will NOT work.

from UPGRADE.txt in the root folder of the 2.2 code:

6.  Remove the old source code, and extract the new source code into the source code directory.

Any additional modules or local customisations you might have installed will need to be separately upgraded to a Moodle 2.2-compatible version.

Hope that helps.