Trouble with X Axis time units in Gantt charts with Mermaid via DiagrammeR

Question

So I can't get any of the fixes (1, 2, 3) I've seen working on RStudio for changing the units of the x axis to days, weeks or months. I dont know how to get this option to work.

Example:

library(DiagrammeR)
mermaid("
gantt
    title Gantt
    dateFormat  DD-MM-YYYY
    axisFormat %d/%m

    section One
    Task One            : 07-05-2019, 7d
    Task Two            : 09-05-2019, 7d ")

It just shows a white window with black text instead of a normal gantt chart.

Without the axis part, it runs just fine.