s!' is not a valid index to enforce a full-text search key. A full-text search key must be a unique, non-nullable, single-column ...

'%1!s!' is not a valid index to enforce a full-text search key. A full-text search key must be a unique, non-nullable, single-column index which is not offline, is not defined on a non-deterministic or imprecise nonpersisted computed column, does not have a filter, and has maximum size of %2!s! bytes. Choose another index for the full-text key.