M2 Pro issues - member payment page appears blank and member can not complete payment

Starting on 10/30/17 - the payment page to complete membership is no longer appearing the page is blank. This is incurring on renewing members and new members. In the past-

To Become a member (under the About>Become an ISAP member) is this page
http://aviationphoto.org/become-an-isap-member/

then the Join ISAP on line button leads us to this page

http://aviationphoto.org/memberships/

normally the client has the one level of membership but we made public a $1 test membership for testing…

after a membership level is selected it goes to this page

http://aviationphoto.org/register/

after you fill out the required fields the site when functioning correctly
opened page to enter payment information through the Paypal Single Gateway.

But since 10/30/17 this page to submit payment and finalize membership just appears blank…

See Screen Shot….

This is causing major problems...
We have granted support access.

PLEASE ADVISE ON A SOLUTION ASAP...

THANK YOU!
Larry Davis