Fix for this issue is now available in the latest update of InDesign 2020 – that is, InDesign 15.0.1
In the Creative Cloud Desktop application, click on the Updates section on the left. You should be able to see the Update available for InDesign. Please update your InDesign application to this version to try out the fix.
Let us know in the comments section if you face any problem with the updation process.
Adobe InDesign Team
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Please find a solution asap. My deadline is fast approaching. I have same situation on Mac and have tried multiple alternatives but none work. In Excel, I reduced all formulas to values, then copy pasted into basic text editor to remove all formatting. I'm going to try reverting back to 2019 InDesign.