I stumbled upon a weird error after upgrading CRM 2013 to CRM 2016, After enabling the option to view the encryption key in an HTTP deployment:

UPDATE [MSCRM_CONFIG].[dbo].[DeploymentProperties]
SET [BitColumn]=1
WHERE ColumnName='DisableSSLCheckForEncryption'

I received the following error when trying to open the encryption key form:

Event Log on the front end server had the following error:

Exception type: CrmException

Exception message: SYSTEM user account not found.

It took me a while to figure it out but it seems that the problem in my deployment was that i had TWO rows of the CRM SYSTEM user in the SystemUserBase table! all the way from 2013 to 2016 and it looked like that:

select * from SystemUserBase where fullname like '%system%'

They were both created at the same second just a few milliseconds apart – Have no idea how & why.

Solution:

Delete the second user using the following query:

Delete FROM systemuserbase 
WHERE SystemUserId ='youruserguid'

After that – I was able to open the form and insert an encryption key properly.

Important: Tempering with the DB is unsupported by Microsoft so do this at your OWN RISK – Don’t forget to backup your DB before!

Michael