RPS MAC Removal

[buergstein]

I desperately hope anycone can help me here.

I´ve got more than 30 Yealink T54Ws that cannot be registered in my NFON cloudbased telephone system because the MAC doesn´t seem to be free. I factory resetted the devices and they do not register to their former telephone system (Starface) anymore. Starface says they do not exist anymore there.

I tried to use Yealinks MAC REMOVAL under https://ticket.yealink.com/portal/mac-removal. I can enter just one MAC/serial or upload a CSV containing multiple devices, when it comes to the point to fill the fields in the RPS authentication windows, I always get:
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RPS authentication failed, please enter the correct RPS account & password or AccessKey ID.

Please confirm you can use the RPS account & password to log into https://dm.yealink.com/ and can see "Management Cloud Service - RPS" on the top left of the page.
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Where is the mistake. I tried to open tickets with the support, but they do not react.

I must deregister these devices in order to use them as elements in NFON.

Is there like an e-mail adress I could send the list to in order to remove the MACs from the database?