After upgrading to 2020 September version I cannot open any of my old pbix files. The error shown is "sequence contains no matching element". I remember that I had the same problem earlier, when "enhanced-metadata-format" feature was in preview. At that time I turned off that preview and everythinf was OK.
However in the latest PowerBI there is no possibility to switch that new format off, so I am stuck with unusable files. I found earlier Install (downloaded on 2020-07-29) and this version opened all files successfully. If I turn on "enhanced-metadata-format" feature in that version - I cannot open files again. So I am sure that the problem is that "enhanced-metadata-format".
I tried to download a version of report saved earlier in "My workspace" on web PowerBI ("download pbix file") but the result is the same: I cannot open my files in September 2020 version and the same error occurs "sequence contains no matching element"
I tried to save pbix file as template (pbit) and then trying to open it with enabled "enhanced-metadata-format". No luck: file opens, but refresh is not working ("sequence contains no matching element" errors) and red warning shows up, that "report has not been upgraded to the enhanced metadata format" and I cannot make any changes.
What is the solution to open old files in latest PowerBI version (September 2020) or to convert them to new format?
I cannot imagine remaking all my files and dashboards from scratch in "new" version. This is MAJOR design flaw / bug (call it however you want) and this is unacceptable to use in production environment when updates break functionality to total zero.