Ubuntu 16.04
Linux foobar 4.4.0-142-generic #168-Ubuntu SMP Wed Jan 16 21:00:45 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
apache2 - 2.4.18-2ubuntu3.10
libapache2-mod-php 7.0+35ubuntu6.1

Version 4.2.2 is also affected

It is very possible, you have an issue with the fonts.
I can suggest you to take a look at ZBX-12690 or ZBX-14740.

Maybe https://support.zabbix.com/browse/ZBX-16180

Seems like the problem was caused by changes in ZBX-15905.
In scope of this changes the fonts directory was moved from frontend root folder /fonts to assets/fonts.

As a result, if you had a manually created symlink, it may be now broken.

Additionally, as answer to Kolunchik, I will note that from 4.0.8 you need to manually add write permissions for web server user to /assets directory.

Confirm this issue exists in CentOS packages as well.

As it was found out, there was an error in packages.

New version of packages will be created.

_{cp /usr/share/zabbix/fonts/graphfont.ttf /usr/share/zabbix/assets/fonts/}

_{chown -R www-data:www-data /usr/share/zabbix/assets/}

_{chmod -R 744 /usr/share/zabbix/assets}

Resolved on my 4.2.2

While the chmod will work on non-selinux systems, it will not on selinux based systems. Zabbix should provide a selinux policy package too (I can already provide the basic pp for it if so desired).

I've uploaded a diff that fixes the packaging issues that caused graphs to appear without text (zabbix-4.0.8-packaging.diff).

I also tried to fix some of the lintian issues with the packages...  However, I was not successful in getting all of them fixed.

Thanks!

I was having the same problem. @Someuser you save my life, Tks. Your solution worked perfectly.
Obviously with some changes because I use RHEL and not Debian (or derivatives)

For all, the Zabbix packages installed in my CentOS 7 are:

zabbix-get-4.0.8-1.el7.x86_64
zabbix-release-4.0-1.el7.noarch
zabbix-server-mysql-4.0.8-1.el7.x86_64
zabbix-web-mysql-4.0.8-1.el7.noarch
zabbix-web-4.0.8-1.el7.noarch
zabbix-agent-4.0.8-1.el7.x86_64

Thank you very much

Symlinked the file as I don't like duplicates

ln -s /usr/share/zabbix/fonts/graphfont.ttf /usr/share/zabbix/assets/fonts/

This was in 4.2.2

You can just move the files.  No need for links

Same issue here. Upgraded from 4.0.x to 4.2.2. And I have from the beginning made sure not to touch anything in the file structure and this happens anyway. So this is a upgrade bug. Using Zabbix repository deb files for Ubuntu 18.04.

Just to add to this, also seeing this in the 4.2.1 > 4.2.2 upgrade process that we performed today. We now have no labels on classic graph widgets on our dashboards:

Once the font file was copied from /usr/share/zabbix/fonts to /usr/share/zabbix/assets/fonts, the problem resolved.

Same problem here. I am on Ubuntu18.0.4 LTS.

Seems to be fixed with 4.0.9.

Fixed in versions 4.0.9 and 4.2.3