Just as an FYI for in case someone else runs into this issue:
Certain entities in the Outlook client just don't load even though other ones work fine. It usually only happens for one or a few users. When you click on the specific entity (or entities) in CRM for Outlook you can get
“CRM failed to load.” (but all other entities load fine)
“There was an error displaying the records in this view.”
You get just a blank white screen in the frame that never loads.
In addition to the above symptoms, you might also get an error containing "Object reference not set to an instance of an object."
Deleted custom fields used as columns in pinned Advanced Find views. The grid can’t load because the view can’t load because it can’t complete the SQL query of a field that doesn’t exist.
Create a searchable custom field.
Create an Advanced Find with the custom field as a column.
In the Outlook client, in the entity, pin the Advanced Find view containing the custom field as a column.
Delete the custom field from the entity fields section of the CRM Solution.
Click on the entity in Outlook. It should show the symptoms mentioned above.
Remove the deleted field column from all advanced find views for that entity.
Go to Advanced Find Saved Views for the entity having the issue.
Check all columns for each System and Personal View. You should look for a column(s) that have a yellow yield sign symbol and a GUID (instead of a display name). The GUID is referencing the deleted field that no longer exists.
Delete the column and save the view.
Which has some other causes:
Cause 1: Google Chrome browser issue.
Cause 2: Compatibility mode is set for Outlook.
Cause 3: Needed CRM privileges do not exist.
Cause 4: Two different Outlook versions are installed.