Hi @DB365-3161 ,
Welcome to our forum!
Based on my test (with the same setting on Outlook for Web as yours), i can delete the individual email of the conversation successfully, which didn't reproduce your case. Please confirm if you delete the email with the following steps:
1.Select the individual email of the conversation.
2.Click the Delete button.
Then the email will be deleted and disappear in the conversation. The below prompt will appear.
If you did the same steps but nothing happens, it's suggested that you could try to open the InPrivate Windows and do the same test to check if there're any differences.
In addition, in order to further confirm if the issue is related to your current browser, please try to use other browser to check if the issue persists.
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