Hi,
Thank you for posting your query in our community.
Based on your description, the linked chart in PowerPoint file will not update.
I followed your first two steps, and then edited on the Excel chart file, the linked chart updated automatically in the PowerPoint. Please note that I opened both files during
the process.
And if I closed the PowerPoint file and edited on the Excel chart file, then re-opened the PowerPoint file, the below window will pop up, and I clicked "Update Links", then
the chart will be updated.

Since I can't reproduce the problem on our side, to help you better, could you please provide some information for me?
- The screenshot of your Office version(open Excel/PowerPoint> File > Account >capture a screenshot of the Product Information column).
- Where did you save these files(Both Excel files and PowerPoint files)?
- If you go File > Info > Edit links to Files, select the link and click "Update now", will the charts be updated?

Appreciate your cooperation in advance.
Best regards,
Jazlyn