Thanks for reaching out to Qlik via Qlik Community Support page. As the mentioned Error "RetCode: SQL_ERROR SqlState: HYT00 NativeError: 0 Message: [Microsoft][SQL Server Native Client 11.0]Query timeout expired Failed (retcode -1) to execute statement: '"
It seems where ever the query is executed ( Source/Target endpoint) QR task is not able to get the info in defined time limit and through the error about timeout expired Failed (retcode -1) to execute statement:
However, there are otherfactor which may pertain to it. hence request you to engage TSE vIa Support case for further analysis.
Request you to upload the diagnostic package/log/DDL and attached the relevant info/files to the case.