> The upgrade process is starting...
> Precondition "correct database layer mode"... OK
> Precondition "toolset_associations table exists"... OK
> Precondition "toolset_associations_old table is not yet present (indicates manual database manipulation)"... OK
> Precondition "toolset_associations_new table is not yet present (indicates interrupted upgrade process)"... OK
> Precondition "toolset_connected_elements table is not yet present"... OK
> Precondition "able to create a new database table"... OK
> Precondition "able to delete a database table"... OK
> Precondition "WPML not active or in a good version (4.4.0 or above)"... ERR
Base on this issue you're having it is saying that you require wpml 4.4 or higher to continue. Checking on your debug information it would appear that you have wpml 4.3.15 which is below the minimum required.
Please update to the latest version of WPML and let me know if everything is ok now.