Also just add another login name for a user, result in  “Value cannot be null.”

It sounds like your portal / enterprise / server or Database have not been updated equally or maybe one component did not have the updates correctly?

I would do a manual update to make sure they are all 100% correct.

Remove all SolidCP/WebsitePanel stuff, from our Exchange server, and installed it again, that help.

Now everything is working. Thx a lot for you help.