C++ Code:

                        QSqlQuery queryBlock;
                        queryBlock.prepare("SELECT addBlock(?,?,?,?,?);");
qdbg() << "muintDatasetID: " << muintDatasetID;
qdbg() << "   strFilename: " << strFilename;
qdbg() << "  muint64Block: " << muint64Block;
qdbg() << "   bytaryChunk: " << bytaryChunk.length();
qdbg() << " uint8Checksum: " << uint8Checksum;
                        queryBlock.addBindValue(muintDatasetID);
                        queryBlock.addBindValue(strFilename);
                        queryBlock.addBindValue(muint64Block);
                        queryBlock.addBindValue(bytaryChunk, QSql::Binary);
                        queryBlock.addBindValue(uint8Checksum);
                        if ( Trainer::queryDB(queryBlock) == true )

My stored procedure:

CREATE DEFINER=`root`@`localhost` FUNCTION `addBlock`(
      `_biDataset` BIGINT,
      `_txtFilename` TEXT,
      `_intBlockNo` INT,
      `_binChunk` LONGBLOB,
      `_intChecksum` INT
)
RETURNS bigint(20)
LANGUAGE SQL
DETERMINISTIC
CONTAINS SQL
SQL SECURITY DEFINER
COMMENT 'Adds a single data block'
exitProc:BEGIN
#Function:        addBlock
#Parameters:      _biDataset     Optional, Dataset In/Out number
#                 _txtFilename      File name of RDF dataset
#                 _intBlockNo       Block number (base 0)
#                 _binChunk         Large Binary Blob of Data
#                 _intChecksum      8 bit CRC
#Notes:           Creates single record of data block
#History:         2021/05/19  Written by Simon Platten
      #Validate parameters
      IF _txtFilename IS NULL OR
         _intBlockNo IS NULL OR
            _binChunk IS NULL OR
            _intChecksum IS NULL THEN
      #No, abort!
            RETURN -1;
      END IF;
      IF _biDataset IS NULL THEN
      #Look up the dataset id
            SELECT
                  `biPK` INTO _biDataset
            FROM
                  datasets
            WHERE
                  txtFilename=_txtFilename;          
      END IF;
      #Was dataset located?
      IF _biDataset IS NULL THEN
      #No, abort!
            RETURN -2;
      END IF;
      #Insert new record
      INSERT INTO `rdf` (
            `biDataset`,
            `intBlockNo`,
            `intChecksum`,
            `binChunk`
      ) VALUES (
            _biDataset,
            _intBlockNo,
            _intChecksum,
            _binChunk
      );
      RETURN LAST_INSERT_ID();
END

Output to console:

muintDatasetID: 1
   strFilename: 20211004_11h42_LabTest_tvg5000_0.rdf
  muint64Block: 0
   bytaryChunk: 34390236
 uint8Checksum: 18

This code previously worked when I was dealing with a BLOB, now I've changed the stored procedure and table types from BLOB to LONGBLOB it errors, with no sensible error message I can post. What could the problem?