I was trying to add new entries by editing the XLSX and importing, and I got the error message: Error - Invalid cast from 'System.String' to 'System.TimeSpan'
To troubleshoot I re-exported to a new file and without making ANY changes (or opening the new file) I simply re-imported it. Same thing.
I am using Microsoft 365 subscription with standalone Office images (vs online) Excel Version 2111 (Build 14701.20226 Click-to-Run)
Fixed in the latest beta
Thanks for reporting