Problem of order status updated without TCPDF and memory limit

[ZangiefJ]

HI:

I use VM 3.0.12 + Joomla 3.4.8.

There is one weird situation that if some payment method with the default order status are "confirm by shopper" and "shipped", and I take these method to confirm order, I get blank, but actually in backend->order list, I can found this order, customer just see blank.

After check again and agin,

I found that's because in configuration->email->"Default Order Status to send email to shopper" and "Default Order Status to send email to vendor", what order status I set in, these status will cause the blank.

For example, if I set "confirm by shopper" in field<Default Order Status to send email to shopper> and I set "confirm by shopper" is default order status of A payment method. Go to front store, someone confirm order with A payment method, BLANK; Otherwise checkout with those payment method which order status is not confirm by shopper, confirmed SUCCESSFULLY.

I did search that most problem is TCPDF cannot support PNG(I did make logo and banner into jpg already) and memory limit(mine is 512mb), but now my problem is in<Default Order Status to send email to shopper/vendor>

To solve this problem, I just set"NONE" in field "Default Order Status to send email to shopper" and "Default Order Status to send email to vendor", but in this way no matter what order status, my client won't get any notification mail......

[Studio 42]

What give your php error log ?
Blank page can only be debugged on having this log error.
And don't forget to install tcpdf provided by VM, if it's not already installed in Joomla