Hi Maria,
Please go to the Excel menu and choose About Excel. This will tell you what update level you have. The current general release build is 16.9.1, as Bob mentioned.
If you have made charts from PivotTables in Excel 2016 for Mac, and the chart was made in a version prior to version 16.9, the chart is a regular chart, not a PivotChart.
If you have made charts from PivotTables in Excel 2016 for Mac, and the chart was made in a version 16.9 or newer, the chart is a PivotChart.
Version 16.9 introduces an entirely new object model to Excel for Mac. Internally, Office was updated from the 2010/2011 object model to the same object model as Office 2016 for Windows. That's a giant step forward all at once. Bob is correct that this giant change requires changes to the interface, and Microsoft is making those changes as we speak.
I'm on Insider Fast and we got a new build this morning. I made a PivotChart from a PivotTable to test. Yesterday, I could not format a PivotChart. There was no design tab and no Format option in the right-click contextual menu. This morning I still don't see the design tab on the Ribbon, but Format is now available on the right-click menu. I can now format the PivotChart. Here's a screen shot:
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My point is that the lack of formatting capabilities will be temporary, again as Bob pointed out. The problem is a classic "chicken or egg" problem in that they can't build the interface until the new object model is operational. Now that the object model is operational, they can build the interface.
I am sure Microsoft would very much like it if you could participate in Insider Fast right now, as they are building these features and could use real-live people to test them as they are built. Insider Fast builds are pre-beta, have undocumented new features (like this one), are large downloads weekly (or sometimes even more often). They also have undiscovered bugs, which you should report when you encounter them. More information about the program is here:
What is Office Insider? - Office Support
If the new behavior is putting an axe on your productivity, I recommend that you uninstall Office and then reinstall a version prior to 16.9. If you need instructions on how to do that, please reply.
BTW - PivotCharts in Excel for Mac still don't display filter buttons. That functionality is also under construction and will appear first in Insider Fast.