Hi,

Try to uninstall and re-install the package. You can follow the below command.

sudo wget https://github.com/wkhtmltopdf/wkhtmltopdf/releases/download/0.12.5/wkhtmltox_0.12.5-1.bionic_amd64.deb

sudo dpkg -i wkhtmltox_0.12.5-1.bionic_amd64.deb

sudo apt install -f

Hope it helps

Try fireing these commands in terminall (your server)

sudo apt install ttf-mscorefonts-installer
sudo fc-cache -f -v