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now that I thought of it, this forum isn’t really helpful as promised.

This is a WordPress support forum, run by volunteers.

And for that, it’s awesome.

In fact, many people are humbled by the kind of support they receive here for free when their theme/plugin vendors and hosts they’re paying month after month are unable or just refuse to help them.

It’s not a server administration forum.

Was your “fix” in anyway related to WordPress at all?

As a WordPress user, I appreciate your help @anthonykung

@anthonykung, I had this same issue. My question is this: how did you discover which module was missing? I’m running on FreeBSD and apparently lots of PHP modules that are installed by default on Linux are missing here. I’ve had to install quite a few, gd being just the latest. In all other cases, I found errors in the Apache error log for the web page which indicated a missing function. I’d then Google around to find out which PHP module that function is in, add it, restart Apache, and poof, fixed. In this case, however, there was no error listed so I was lost until I found your post. So… how’d you figure it out?

@anthonykung Thank you, your post helped me finally after I wasted around 8 hours fighting with this unknown dependency.

The problem with this kind of issues is that, wordpress hides the OS error messages and just tells you “there has been problem”. That is a damn dead-end! If there is no proper documentation at codex, I have to google it, search through and filter all the responses for an answer or just read the core code all by yourself and figure it out. If I have so much time, why would I even choose wordpress unless I am making use of some powerful features which are most essential for my site ? For example, for next static site, I would probably go with some Html5 template if I need to do a quick job.
I can understand the frustration and it is in no way to put down the wonderful help of volunteers do.

@thorak01 Thank you for your link to stackexchange question, I also found that I need php-ssh2 library. There are many out-dated answers there, so here is a quick summary of what I did. I use wp-cli i.e. wp command line utility on ubuntu.

$  wp install git@github.com:johnbillion/ext.git
$  wp ext check 
# This prints all the recommended php extensions.

+-----------+-----------+
| extension | installed |
+-----------+-----------+
| mbstring  |           |
| ssh2      |           |
| curl      | 1         |
| date      | 1         |
| dom       | 1         |
| exif      | 1         |
| filter    | 1         |
| ftp       | 1         |
| gd        | 1         |
| hash      | 1         |
| iconv     | 1         |
| imagick   | 1         |
| json      | 1         |
| libxml    | 1         |
| mysqli    | 1         |
| openssl   | 1         |
| pcre      | 1         |
| posix     | 1         |
| SimpleXML | 1         |
| sockets   | 1         |
| SPL       | 1         |
| tokenizer | 1         |
| xml       | 1         |
| xmlreader | 1         |
| zlib      | 1         |
+-----------+-----------+

sudo apt install php-ssh2
sudo apt install php-mbstring
sudo systemctl restart apache2

Hope this helps few others too.

Hey thanks… that was a really useful tip. and thanks for resolving your own question!