Good day! I'm Raniel, a Microsoft user like you. I understand your frustration regarding this issue and I'll do my best to help.
Just to clarify, did you also make any changes to your machine before encountering this issue? Have you also tried to rename the extension of the file to .jpeg?
Another option is to open them in MS Paint, then convert/save it to .jpeg format. You may also refer to the additional methods on this article as well:
https://www.intowindows.com/4-ways-to-open-webp...
https://www.howtogeek.com/325864/how-to-save-go...
If that didn't work, perform a reset of Microsoft recommended defaults:
Go to Windows > Settings > Apps > Default Apps > scroll down and click on Reset under "Reset to the Microsoft recommended defaults".
I hope this helps. Good luck!
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