Why can’t I buy stuff from Mercari?

ただいま利用制限中です
（制限されている機能）

出品/購入 いいね！/コメント/プ ロフィール
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I am an exchange student in Japan (I arrived in September) I have a Japanese phone number from Rakuten Mobile. The first time I used mercari everything went smoothly, but after that this message kept appearing and I could not buy anything.

I verified my identity but it still kept appearing. I know it is not due to the 6 month stay thing because my friends who were in Japan last year didn't have a problem.

Please help me!