We have heard of a few users experiencing problems when going to "OptimizePress > Create new page" and clicking the "preview template" link - the lightbox that comes up is showing blank / white instead of showing the template preview.
This issue can happen for a number of reasons:
1. Check your WordPress address URL and Site Address URL
You should go to Settings > General and check that your WordPress URL and Site URL match including the http or https. If your site is HTTPS secured, you should ensure you use https here
2. Your database tables may need fixing
Occasionally we have seen issues where tables in your database which store the template data have not been created properly when you installed OptimizePress
Our team have a special process to help fix this, if you contact us and include your WordPress site URL and Wordpress administrator logins we can help fix this for you.