Like the people already mentioned in the comment sections, you will have to use a different font containing these special characters.
The font you are using does not seem to support these characters, you can download any other font that contains these characters. The character 'u26BF' is a square box in some default fonts ( source ).
You can find different fonts and even try them on DaFont and, as @SubOptimal warned, check the licenses and download and use it before you.
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