I am trying to use Difference-in-difference FE function under statistics - treatment effect menu.

Here is my data information
Time variable: year
Group variable: country
Group dummy: KT
Treatment dummy: PA

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With this data, when I tried DID function, I get error message like below trying with group variable "countryname" or "KT"
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Error message is saying,

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Please kindly help me to figure out this issue.
Thank you for all your help in advance.