I booked support hours with you and you configured it correctly.

though booking an hour is a good solution. could the solution be shared here since i think there are more encountering the same error. and oh i emailed if i can have that 1 hr of support. have not heard from support yet

just to add , i changed the template for fresh slave multisites to copy the installation folder but it does not copy to the newly created directory in the multisite folder.

Personnaly, I don't remember what I did for this customer - So if he remember and can reply to the question, that would be great.

In general a "blank page" is resulting from a PHP Fatal error that can retreived in the "error_log".
When the PHP Fatal error is located, after that, this is more easier to do a diagnosis.

So there is no single answer to such kind of error and this is frequently related to a problem of permission.