When in Lightning and trying to click on 'Generate' Temporary code - that can temorarily be ued instead of MFA if user doesn't have thier mobile device, I get an error "This page has an error" or "You don't have access to this record. Ask your administrator for help or to request access.".

Can someone please enlighten me what access am I missing as the System administrator? 
Something in Identity verification? 
It is working in the Classic UI fine, the error is just in the Lightning UI.
Any advise is welcome!

When in Lightning and trying to click on 'Generate' Temporary code - that can temorarily be ued instead of MFA if user doesn't have thier mobile device, I get an error "This page has an error" or "You don't have access to this record. Ask your administrator for help or to request access.".

Can someone please enlighten me what access am I missing as the System administrator? 
Something in Identity verification? 
It is working in the Classic UI fine, the error is just in the Lightning UI.
Any advise is welcome!