An Individual account can only buy: rent GPUs, buy on the exchange, make reservations and buy hour packs. It can never sell or become a supplier.
Selling (supplier program) requires a Corporate (business) account with a complete billing profile, including a tax number, verified by EverXCloud team.
The type is set in the billing profile (Billing, Invoices tab). An organization with an open supplier profile cannot switch back to Individual.
For questions about your specific case, contact support.