When adding credit card information for the Braintree payment gateway integration in the Developer portal. I managed to suspend my Account by failing OTP auth ten times (this is correct behavior):

<account>
 <id>175</id>
 <created_at>2021-08-09T08:50:12Z</created_at>
 <updated_at>2021-08-09T08:56:26Z</updated_at>
 <state>suspended</state>
 <org_name>jsmolar-1</org_name>
 <extra_fields></extra_fields>
 <credit_card_stored>false</credit_card_stored>
 ...

Currently, I am not able to find a way how to unsuspend this account or to find any information about the reason why it was suspended.

Please see this comment