If IUpgradeable is not running, there is nothing I can do to fix the problem of that nor can I fix the forum completely. Basically, all forum module permissions need to be inserted into the db, all localized "Lists" values need to be inserted into the db, all moderator permissions need to be manually migrated, as well as all previous user permissions.
I did post a thread that is pinned here that does the SQL insert for Lists. For the permissions, you need to run this:
DECLARE @ModuleDefID int
SELECT @ModuleDefID = ModuleDefID FROM {objectQualifier}ModuleDefinitions WHERE FriendlyName = 'Forum'
INSERT INTO {objectQualifier}Permission(PermissionCode, ModuleDefID, PermissionKey, PermissionName)
VALUES('FORUM_MODULE',@ModuleDefID,'FORUMADMIN','Forum Administrator')
INSERT INTO {objectQualifier}Permission(PermissionCode, ModuleDefID, PermissionKey, PermissionName)
VALUES('FORUM_MODULE',@ModuleDefID,'FORUMGLBMOD','Global Moderator')
GO
Running the two items discussed above will fix the fundamental issues but will not transfer any previous user permissions or moderator permissions although you can set those manually. If after running the two items discussed above you still have issues please respond w/ the error messages you are receiving. Please make sure you update the site cache (clear it from host settings, then restart the application), then update the forum module settings before checking for any errors.