Unable to convert User role from Registered user to Business user

Hi

I've created account for partner initially as registered user initially. After LLP incorporation, DIN has been allotted and I'm trying to change user role from registered to business user. I'm getting OTPs but while I'm submitting the OTP it's giving validation error/warning message with no further descripttion. I've tried in different browser, in incognito but same validation message is coming.

Please provide resolution. Thanks in advance!