We've been banging our heads on this problem since yesterday.
We are using a customized version of CMS 6 R2.
At 2 a.m. yesterday morning, the following error suddenly appeared on our website. No code deployments or upgrades occured at that time.
The Type 'EPiServer.Events.Remote.EventSecret' needs to be remapped in the Dynamic Data Store, see the Errors collection for more information.Remapping can be done by applying the EPiServer.Data.Dynamic.EPiServerDataStoreAttribute attribute to the type,setting its AutomaticallyRemapStore property to true and ensuring the autoRemapStores attribute in web.config is set to true (or is not defined).Alternatively call the Upgrade-EPiRemapDDSTypes cmdlet from Powershell.
We tried pretty much everything Google suggested, but to no avail. The site does not load at all, any page shows that exact error. We've tried the Powershell cmdlet, but all types subsequently popup as requiring a remap, but nothing gets fixed.