Could you let us know the specific error message you are getting? Unfortunately, the Apache error log does not seem to contain any message related to that issue.
I can see that the max upload size configured for PHP (at
/opt/bitnami/php/etc/php.ini) is 40MB:
Is it possible that the file you are trying to upload is bigger than that limit? Could you try if increasing that value, restarting the service and attempting to upload again solves the issue? If it doesn't, it would be great if you could generate a new bnsupport bundle in order to help us figure out the root cause of the issue.