If this is a QAD Reporting Framework report, then this is not supported. The underlying 3rd party render engine is limited to the old Excel-binary XLS file limitation of 65.000 rows.
This limitation would be very difficult for QAD to overcome without changing render engines and reqriting a lot of the reportign solution.
I was able to solve the export limitations using the setup in this article of the knowledgebase AA-94723 (https://knowledgebase.qad.com/kmp/article/AA-94723)
It is a workarround for exporting from browses and views. Maybe your report is built on a browse, and you can export your data from the browse instead of the report.