Authorize.net Direct Post - Checkout timeout

[phuc128t]

Preconditions

1. Magento 2.1.2
2. PHP 7.0.8 and mysql 5.7
3. Ubuntu Apache

Steps to reproduce

1. Setup authorize.net direct post with sandbox account or real account but use test mode
2. Add product to cart and process to checkout with test credit card

Expected result

1. Payment goes through and takes customer to success page

Actual result

1. Got "Sorry, but something went wrong. Please contact the seller." message.
   
2. Transaction seems went through but not sure why got that message. Please see log attached post_log.txt response_log.txt
3. This issue seems happening to all magento 2 versions.

[phuc128t]

It seems there are some reported for this issue. I tried some solution suggested here #4813 but no luck. Or we can't test it with sandbox account. My site is under development but still can access from public.

[phuc128t]

Sorry, It seems a custom theme issue.