Please, Thank You and Sorry
Only use "please" if you’re asking the user to do something that inconveniences them. In general, you can reword the error message to avoid "please."
For example, An unexpected error has occurred. Please reupload your file and try again.
or An unexpected error has occurred. Reupload your file and try again.
For very generic error messages, where we are not 100% sure what the user should do to resolve, Please try again
is fine.
Don’t use "thanks" or "thank you."
Reword error messages to avoid using "sorry".