Hello,
i have checked onto your site and found that there is so many 3rdparty plugins installed.
i would suggest you to follow the following and check if it works??
- Please deactivate all installed 3rd party plugins.
- Delete browsers cache especially cache plugin.
- Re-save permalinks.
then check if it starts printing the certificate. if it works then start activating plugins one by one and check again if it stops printing certificate. once that plugin is identified. i would suggest you to not activate that wicked plugin again.
Also please do not use HTML builder, its time taking and an obsolete one. make sure that you are using theme/plugins of version 3.9.7
please try to use pdf certificate builder because it's great.
or download from here and then upload zip file: wplms-pdf-certificates
this plugin is running at 1.9 version.
take full page width of the element then use center align.
tutorials:
1) https://www.youtube.com/watch?v=d9mXInbmFGY
2) https://www.youtube.com/watch?v=ylT1j35dUbg
3) https://www.youtube.com/watch?v=kyJGVlegWTc