This error usually occurs when you have more than 1000 objects in
your Salesforce org. The Visualforce method cannot query more than 1,000 objects for
the Master Object dropdown.
What to Do
Make the following changes to the Salesforce Classic Override
setting:
On the Salesforce homepage, click the gear icon in the right corner
and select Setup.
Go to the Object
Manager tab.
Search and select Conga
Solution object.
Click Button, Links, and
Actions option.
Go to the New
button > click the icon and Edit.
Select the Standard
page option for Salesforce Classic Override.
Click Save.
When you create a new Solution, you must
manually enter the name of the solution in the Conga Solution Name field and
the API name of the object (where you want the button to appear) in the
Master Object Type
field.
Tip:
If you're creating a lot of solution records, change
the Page Layout to rearrange the
sequence of the Master
Object Type field for better usability.