T-SQL DROP TYPE IF EXISTS

Use TYPE_ID

Or query sys.table_types

Please try this, use type_id instead of object_id

IF type_id('[MySchema].[tProjectType]') IS NOT NULL
        DROP TYPE [MySchema].[tProjectType];


CREATE TYPE [MySchema].[tProjectType] AS TABLE
    (
        Id INT
        , IsPrivate BIT
        , IsPublic BIT
    );