The reasons for being restricted from posting may vary depending on the message displayed.

If 'This player cannot be registered' is displayed

This message indicates that the summoner or player account may be under restriction due to a violation of Duo Service policies.
If you would like more details about the reason and duration of the restriction, please contact our Help Center.

If 'Summoner/Player not found.' is displayed

The summoner and player’s data displayed for Duo Service posts is based on OP.GG's database.
As a result, accounts that cannot be properly retrieved on OP.GG may also face restrictions in creating posts on Duo.

In this case, please verify whether the account can be correctly accessed on OP.GG. If the issue persists, provide the relevant account information when submitting an inquiry, and we will assist you promptly.