Dear Albers Dadders,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
According to your translation and the screenshot provided, we know that when you use the Excel web version, you can use the "#*" to find all the "#VALUE" but cannot replace them.
I found the same thing in my tests, replacing "#VALUE" in the web version does prompt an error message:
I noticed that you are using the desktop version of Excel and it works fine, I'm glad you can do your work this way for now. I think this may be a flaw in the replacement features in the web version of Excel. In general,#VALUE indicates that the formula in the cell is invalid or that there is a problem with the referenced cell data. Web versions of Excel may not replace #VALUE as a value, but when you look for it, you may just filter the matching characters and find the data.
We are very sorry for the inconvenience caused by this phenomenon. I completely agree with you, this is indeed a good addition to the current features of Excel for Web, thank you for pointing this out. Microsoft continuously aim to improve the features of O365 Product and suggestions like this is very much appreciated. You can go to Feedback community to create a new entry or vote this entry: Community (microsoft.com)
Sincerely,
Tin | Microsoft Community Moderator