When refreshing a segment or exporting a mailing, this error is shown due to lack of space in the tempdb.
Unable to save keys to static selection table. Could not allocate space for object 'dbo.SORT temporary run storage: 141036665831424' in database 'tempdb' because the 'PRIMARY' filegroup is full. Create disk space by deleting unneeded files, dropping objects in the filegroup, adding additional files to the filegroup, or setting autogrowth on for existing files in the filegroup.
This is an issue with available storage on the TempDB table on the SQL server, and should be addressed by a qualified SQL DBA. If you are hosted by Blackbaud, create a case with our support team.