The domain has clientTransferProhibited status in WHOIS despite the fact that it was not locked manually via RCP or API.
$ whois domain.tld
Openprovider locks all new domains by default for TLDs that support this functionality.
Openprovider decided to enable this feature by default in order to minimise receiving unsolicited transfer requests. By ‘locking’ a particular domain name, the client doesn’t receive any unnecessary requests, as well as staying confident that the domain is safe and sound.
If you wish to transfer-out the domain, go to the detail page of the domain name and click "unlock domain" or request the update via the API.
Be aware that some TLDs (mainly gTLDs like .com, .net .org etc) may not be transferred in the first 60 days after registration or after transfer. This is prohibited. This setting can not be updated via the control panel nor via the support department. The only option is to wait 60 days and initiate the transfer again.