Check if the new user profile photo updated in Teams web client https://teams.microsoft.com, if it updated in web client, the issue is related to local cache, you could follow the steps in the link you provided to clear them:
Quit out of Teams completely.
Navigate to ~/Library/Application Support/Microsoft.
Right-click the Teams folder then select Move to Trash.
Navigate to Keychain Access.
Search for ‘Microsoft Teams’ and delete the entry.
Open Teams and wait for it to download required files.
And here is a thread discussed about the similar issue as yours for your reference as well: Unable to Update Profile Picture
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