I have been playing with Plotly Gantt charts in both frameworks Jupyter Notebooks and Google Colaboratory.
When I tried to used the Gantt samples with a dataframe read from a .csv or an Excel file, I got the an error due to the usage of .ix in the gantt.py module. This error only arose in Colaboratory not in Jupyter Notebook. The .ix usage has been deprecated from pandas version 1.0.0, and in the _gantt.py line 49 is still used.
I switched from Pandas version 1.0.3 to the old one 0.25.3 and I was able to plot properly the Gantt charts in Colaboratory, so it is clear a problem of updating the _gantt.py function in order to make it work with updated Pandas version.