Detail:
i am trying to update the user email using Autolaunched Flow with the help of process builder i am calling flow from process builder and passing values to the flow variable.
The user who is performing the above operation is not having sys admin or modify all permission.
As i know process builder runs in a system mode so the flow also should run in system mode.
Email Deliverability
setting needs to be eitherSystem email only
orAll email
. If it isNo access
, it wouldn't be surprising if that is the error cause in addition to the reason you don't get the error email.