Occasionally users will encounter the following error in Dynamics 365/CRM:

Record is Unavailable

The requested record was not found or you do not have sufficient permissions to view it. If you contact support, please provide the technical details.

And when you check the Log File you find a line similar to:

<Message>systemform With Id = ddcd5da6-1a8b-433d-adf5-605114a9fe29 Does Not Exist</Message>

What has happened here is that Dynamics has cached the Guid of the form with which it wants to display the record for the user, but the form is no longer available.  In my case, usually because I’ve deleted it from underneath them…
The quick fix is this:

    1. Whilst logged on as the user, do an Advanced Find on the entity containing the record which the user was trying to open
    2. Select any record in the list of results
    3. Right-click the selected record, and choose ‘Email a link’
    4. In the resulting email you will get a link similar to this: <>
    5. Ignoring the angle brackets, append “&extraqs=formid%3d” to the end of the URL, and then the GUID of a valid form in the system. So, if the form GUID was 1FED44D1-AE68-4A41-BD2B-F13ACAC4ACFA, the final URL would be:

This will reset the cached form Guid to one that the user can access, and order is restored to the universe…

Note: You can find a valid form URL from the Customizations window, noting that you should probably choose one which the user’s security role has access to…