Numbers file invalid

I am having a similar problem. MacOS 10.15.7 on a mac mini, and Numbers version 11.1 (7031.0.102). I have one specific numbers spreadsheet file containing valuable information. I have been using it for years without a problem. Just yesterday, Numbers started refusing to open it; says "(filename) can't be opened right now". Time machine has dozens of backups of that file, and Numbers will not open any of them. Strangely, I have many other Numbers files, and they open up just fine. I really need help with this.

Were these Number files created using the same Number version as you have running in MacOS Ventura13.4.1?

If not, do you know what version of MacOS or OS10 was in use?

Regards,

Barry

It's hard to know what is happening on your machine.

Have you tried restarting your Mac, perhaps holding shift key down?

SG

You marked your own post as the answer but no answer was given. What solved the problem?