UK merchant seeking API credentials for locker finder and shipping integration #2

Hi InPost team,
I'm a UK-based merchant building a LEGO rental subscription service (tonofbricks.co.uk) and I'm looking to integrate the InPost API for:

Locker finder (api:points:read) to allow customers to choose their collection point at checkout
Outbound shipping (api:shipments:write) to create parcel labels
Returns (api:returns:write) to generate return QR codes for customers
Tracking webhooks (api:tracking:read) to automatically update rental status

I submitted an interest form via inpost.co.uk previously but haven't received a response. The self-service merchant portal at merchant.inpost-group.com is currently showing "Creating organization temporarily disabled".
Could you advise the best way to obtain stage credentials to begin development? I'm based in the UK.
Thanks, Stuart