Hi,
Create another Report and just put a label or any element and try to test this report. if you found no issues then you have to check the report which shows an error on runtime.
Check the elements like Image or QRCode or any element is overlapping... I know this is tedious.. but I also had similar issues in the past and there are no specific clues under the log. But by troubleshooting with removing or putting elements again.. it fixes the issues.