Did you try to change under global setting or individual FortiAP Profile? Can you make sure that you ran the right commands?
It should be noted that, depending upon the version of FortiOS being used, custom AP profiles may need to be deleted before the country default value can be changed. This can be performed through the GUI by going to WiFi Controller > WiFi Network > FortiAP profiles and deleting the profiles. Once the country code has been set, the Custom AP profiles can be reconfigured.
The error message suggests that the name you're trying to use is a reserved keyword. Make sure you're not using any system-reserved names. The error also suggests that there might be a duplicate entry. Check to see if the profile or setting already exists. Since your device SKU is Region A, it might be restricted to use only the country codes available for that region. Make sure 'IN' (India, I assume) is available for your SKU.
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