Problems getting WordFence to work with my site on SiteGround

Hello WordFence Support Engineers,

I have been trying to make WordFence work with my site on SiteGround. I actually have 2 sites there: and with my secondary site it works, but not with my main site.

I get errors like this:

Warning: array_merge(): Argument #2 is not an array in /home/username/public_html_domains/art-of-software-testing.com/wp-includes/load.php on line 63

Warning: Cannot modify header information - headers already sent by (output started at /home/username/public_html_domains/art-of-software-testing.com/wp-includes/load.php:63) in /home/usernamepublic_html_domains/art-of-software-testing.com/wp-content/plugins/sg-cachepress/class-sg-cachepress.php on line 348

Warning: Cannot modify header information - headers already sent by (output started at /home/username/public_html_domains/art-of-software-testing.com/wp-includes/load.php:63) in /home/username/public_html_domains/art-of-software-testing.com/wp-content/plugins/sg-cachepress/class-sg-cachepress.php on line 360

Although these errors are about other plugins, everything works just fine until I install and enable WordFence.

I have set it up by editing php.ini and pasting the exact text shown provided by WordFence. I did not change any WordFence settings from default ones (although it may be possible that some old settings were still in my DB from a previous install of WordFence).

I strongly prefer your solution to other security packages for WordPress. If you can help me figure out how to make it work for my site, I will purchase 2 years of WordFence for my site!

Many thanks,

onTy