Cannot open file since update to InDesign

[Angela23620096zr27]

I created an InDesign document using the 2020 version. The file has an .idml extension from where I created it in an older version of InDesign. I need to update the text, but I get this message now when I try to open it. My InDesign is up to date on updates.

Cannot open the file . Adobe InDesign may not

support the file format, a plug-in that supports the file format may be

missing or the file may be open in another application.

Please tell me there is a way to open this file.

[BobLevine]

Are you sure it's an IDML file? What version of InDesign are you using? If it is an IDML file, where's the original InDesign file? There's no need for IDML unless you're going backward.

[Angela23620096zr27]

I'm positive it's an IDML file as I created it myself. 

[BobLevine]

It's either corrupt or something is wrong with your set up. Can you post the IDML somewhere so we can look at it.?

[defaultl2dcn3pi5o8u]

Save the IDML as an INDD in the version of InDesign it originated from. Then open it in the newer version letting it convert over for the new version.

[Angela23620096zr27]

How do I go back to an older version of InDesign after upgrading? Thanks for the suggestion.