Cannot See Collaboration Changes in iCloud Numbers

Because Apple doesn't allow older iMacs to collaborate through the app, we are forced to use the iCloud version of the Numbers app when collaborating. I have a Joint Expenses spreadsheet with my kid's mom so we can track expenses then split the difference if needed. I cannot see her changes to the spreadsheet, neither on iCloud.com or on the Numbers App on my phone, but she can see mine.

Any suggestions on how to remedy the issue?

(I am not upgrading my computer, it works perfectly fine. I have looked at all of the settings I can find to make sure collaboration is enabled, but there is very limited ability using iCloud. My phone is updated and using the latest iOS.)